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Conus consobrinus consobrinus (Sowerby I, 1850)
Conus consobrinus toroensis (Olsson, 1922)
Conus consobrinus ultimus (Pilsbry & Johnson, 1917)
Conus lavillei (Cossmann, 1913)
Conus scaliae (Bose, 1906)
Descrizione e caratteristiche (4):
Of medium size, elongate, moderately wide at shoulder. Shoulder sharply angulated. Anal fasciole slightly sloping, producing an almost square shoulder. Spire high and its profile almost smoothly conical, or moderately high and its profile slightly concave. Protoconch and earliest post-protoconch whorls missing. Shoulder of all except last, or last two, spire whorls strongly tuberculate; tubercles gradually disappearing. Anal fasciole concave, bearing faint or distinct spiral threads. Lower part of body whorl weakly sculptured; Height 61,7 mm., diameter 30,3 mm. (4).
Conus consobrinus consobrinus has a meager representation in the Gatun formation: two specimens from the lower part, two from the middle part, and one from the upper part in the western area (4).
Cossmann's Conus lavillei, collected along the canal at Mindi, where the upper part crops out, is identified as an exceptionally slender, immature specimen of this form (4).
The two shells from the lower part, one of which is shown on plate 56, figures 3, 7, and one from a horizon near the base of the middle part are relatively low- spired: an exceptional feature (4).
The large shell from the middle part in the western area ( pl . 56, fig . 9 ) is the only one that is fully mature. Its spire is somewhat worn (4).
Gatun specimens are almost square-shouldered, as are most others from mainland localities. Those from Jamaica are round-shouldered and so are most of those from the Dominican Republic (4).
Bose's illustration of the Mexican C. scaliae ( Böse, 1906, p. 51 , pl . 5 , figs. 41 , 42 ) suggests an immature C. consobrinus. His type (height 15.2 mm ), however, lacks spiral sculpture on the anal fasciole (4).
That C. consobrinus consobrinus is found in deposits of middle Miocene age in the Tehuantepec area is shown by Perillat Montoya's illustration and by a specimen in the collections of the U. S. National Museum ( USGS 10346 ). The high, or moderately high, strongly tuberculate spire is a diagnostic feature of C. consobrinus. The type material ( lectotype ) has been designated and illustrated recently by Pflug. The nominate subspecies occurs in deposits of middle Miocene age (4).
The lineage is continued by an almost square-shouldered form that has a tuberculate shoulder throughout, even on the body whorl of specimens that have a height of 50 mm. This form is C. consobrinus ultimus Pilsbry and Johnson ( Pilsbry, 1922, p. 330, pl. 20, fig . 8 ). It first appears in the late Miocene Limón formation of southeastern Costa Rica and continues in the Pliocene Moín formation of that area (4).
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Conus consobrinus toroensis (Olsson, 1922)
Shell of medium size, with a conic spire a little more than ½ the length of the aperture; the whorls of the spire numbering 12 plus are flat or slightly above the suture; this carina on all except the last whorl bears low nodes, about 20 to the later whorls; the spire-whorls are otherwise smooth except for the arcuate growth lines; the last whorl is a tapering cone, nearly smooth, except for the faint spirals about its lower one-third; the aperture id narrow, straight, with a thin arcuate outer lip. Height 45 mm., diameter 21 mm., aperture 33 mm. This shell belong to the Conus consobrinus group, agreeing in its form and strongly nodulated spire whorls. The main difference is that toroensis is nearly smooth, the spirals showing only on the lower one-third, while consobrinus has most of the last whorl covered with beaded spirls (6).
C. torensis Olsson ( 1922, p. 48, pl. 2, fig. 7 ) may be treated as a weakly sculptured late Miocene subspecies (4).
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C. emersoni Hanna ( 1963, p. 25, pl. 1 , fig. 2 ), dredged off Cape San Lucas, Baja California, is probably a descendant of C. consobrinus. It is round shouldered and lacks tubercles on the shoulder of the body whorl , and therefore is similar to C. consobrinus consobrinus (4).
Occurrence:
Lower, middle, and upper parts of Gatun formation (middle Miocene). Lower part, locality 138c. Middle part, eastern area, locality 139d ; western area, locality 161b. Upper part, eastern area, Cossmann's record ; western area , locality 185. Middle Miocene deposits, Darién area ( small race , USGS 8430, 8477 ) , Panamá.
Agueguexquite formation ( middle Miocene ), Tehuantepec area , México.
Bowden formation ( middle Miocene ) Jamaica. Gurabo formation (middle Miocene ), Dominican Republic.
The
high straightly conic spire with coronate whorls is distinctive. In
large specimens from one to two, or rarely three, latest whorls are
without nodes. Spiral sculpture of the last whorl is variable and in
adults generally restricted to the lower half. In some young
specimens the last whorl is covered with spiral threads, partly
granose. The posterior sinus of the aperture is very deep. There is a
large series of various ages in the Gabb collection. Also found in
the Bowden formation, and in a modified form it existed into the
Pliocene (3).
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Conus lavillei (Cossmann, 1913)
Taille moyenne; forme élancée, biconique; spire élevée, crénelée, à galbe très faiblement extraconique au sommet qui est terminé par une protoconque lisse et polygyrée; dix ou onze tours anguleux en avant, excavés sur la rampe comprise entre cet angle et la suture inférieure qui est finement rainurée et ondulée; le bourrelet saillant compris entre l'angle et la suture supérieure est orné d'une vingtaine de crénelures subnoduleuses, à peu près égales aux interstices qui les séparent, et traversées par trois filets spiraux obsolètes; sur la rampe on n'aperçoit que les crochets incurvés qu'y forment les accroissements du sinus; cette rampe a une hauteur égale au double de celle du bourrelet, et la hauteur totale du tour atteint le quart de sa largeur mesurée sur le bourrelet antérieur. Dernier tour inférieur aux cinq septièmes de la hauteur totale. à galbe un peu convexe en arrière, un peu excavé en avant; au-dessus du bourrelet crénelé, il y a d'abord une étroite bande lisse, puis des filets spiraux qui se serrent davantage à mesure qu'ils s'élèvent sur la base; mais, sur la région antérieure, ce sont au contraire des cordons obliques et espacés par de larges sillons très finement décussés par les stries d'accroissement; les derniers cordonnets sur le cou sont enfin plus resserrés et séparés par de simples stries. Ouverture étroite, à bords à peu près parallèles; labre convexe et mince, peu profondément échancré en arc sur la rampe inférieure; columelle rectiligne, un peu tordue en avant; cicatrice pariétale obsolète, limitant une callosité dans l'angle inférieur de l'ouverture.
Dimensions. - Longueur : 37 mill.; diamètre : 14 mill.
Rapp. et différ. - L'espèce la plus voisine, dans la même région, est C. gracillimus Guppy (1), de l'Aquitanien de la Jamaïque; mais C. lavillei s'en distingue à première vue par sa spire plus élevée et plus grossièrement crénelée, ainsi que par son dernier tour moins régulièrement sillonné: on s'en rendra compte par la comparaison de la fîigure que je crois utile de publier pour C. gracillimus (Pl. IV, fig. 13), ma coll. Quoiqu'il appartienne au même Sous-Genre Conospira de Greg., C. lavillei n'a aucune analogie avec le génotype C. Brocchii Bronn, ni avec C. antediluvianus Brocchi, dont le dernier tour est à peu près lisse, et qui caractérise le Néogène d'Europe, dans tout le bassin méditerranéen.
Localité. - Mindi (canal de Panama), type (Pl. IV, fig. 1, 2), coll. de l'Ecole des Mines.
Medium size; slender, biconical shape; high, crenellated spire with a very slightly extraconical curve at the apex, which terminates in a smooth, polygyrate protoconch; ten or eleven angular whorls anteriorly, excavated on the ramp between this angle and the lower suture, which is finely grooved and undulating; the projecting ridge between the angle and the upper suture is adorned with about twenty subnodular crenellations, roughly equal in length to the spaces between them, and crossed by three obsolete spiral filaments; on the ramp, only the curved hooks formed by the growths of the sinus are visible; this ramp has a height equal to twice that of the ridge, and the total height of the whorl reaches a quarter of its width measured on the anterior ridge. Last whorl less than five-sevenths of the total height, with a curve slightly convex posteriorly, slightly excavated anteriorly; Above the crenulated rim, there is first a narrow, smooth band, then spiral filaments that become closer together as they rise at the base; but, on the anterior region, these are, on the contrary, oblique cords spaced by broad grooves very finely decussated by growth lines; the last cords on the neck are finally more tightly packed and separated by simple striae. Aperture narrow, with roughly parallel edges; labrum convex and thin, shallowly notched in an arc on the lower ramp; columella straight, slightly twisted anteriorly; obsolete parietal scar, delimiting a callus in the lower angle of the aperture.
Dimensions. - Length: 37 mm; diameter: 14 mm.
Relationships and differences. - The closest species, in the same region, is C. gracillimus Guppy (1), from the Aquitanian of Jamaica; But C. lavillei is distinguished at first glance by its taller and more coarsely crenate spire, as well as by its less regularly grooved last whorl: this will be evident from a comparison with the figure I believe useful to publish for C. gracillimus (Pl. IV, fig. 13), my collection. Although it belongs to the same subgenus Conospira de Greg., C. lavillei has no analogy with the genotype C. Brocchii Bronn, nor with C. antediluvianus Brocchi, whose last whorl is almost smooth, and which characterizes the Neogene of Europe, throughout the Mediterranean basin.
Locality. - Mindi (Panama Canal), type (Pl. IV, fig. 1, 2), collection of the École des Mines.
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Conus scaliae (Bose, 1906)
Concha
pequeña, forma de huso, compuesta de 6 vueltas y un protoconco de
probablemente 3 vueltas. La espira es medianamente alta, la quilla
está adornada con gránulos, la superficie de la espira no tiene
otros adornos. La sutura está casi invisible, no canaliculada sino
formando sólo una línea delgada que por las granulaciones de la
quilla parece algo ondulada. En la última vuelta vemos en la parte
anterior unas nueve costillas espirales, bajas, redondas, apenas
perceptibles. La abertura es larga y angosta, el labro delgado y
sencillo (no completamente conservado).
Dimensiones: altura,
16mm.; ancho, 7.2 mm.
Nuestra forma se parece por su adorno á
C.
solidus y C.
stenostoma pero se distingue luego por su forma y la altura y
ornamentación de estas especies.
Encontré un solo ejemplar en
Tuxtepec.
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Conus
consobrinus ultimus
(Pilsbry & Johnson, 1917)
Shell more squarely shouldered then C. consobrinus, and with tubercles extending upon the angle of the last whorl.
Costa Rica. Pliocene.
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Bibliografia Consultata
