Conus talis (Jung, 1965)

Descrizione e caratteristiche:

Shell small, stout. Spire moderately high, flat in profile as a whole, the single whorls, however, with a considerable concavity. Protoconch high, consists of three smooth volutions, the two last of which have nearly the same diameter. Postnuclear whorls nine, none of them carrying beads on the sometimes sharply keeled shoulder. Ornamentation above shoulder of deep opisthocyrt growth lines which produce the anal notch but of no spiral threads. Surface of body whorl nearly straight, slightly convex in the upper part, more or less concave towards the base. Siphonal fasciole somewhat bulging. Spiral sculpture on lower portion of body whorl consists of ten to 14 grooves of varying width, the uppermost ones generally narrow with wide interspaces followed medially by wide grooves, which become narrow towards the siphonal fasciole. Growth lines below shoulder prosocyrt. When especially conspicuous they may set off the spiral grooves ⁽¹⁾.

Holotype. — Basel Natural History Museum, No. H 13824.

Dimensions of holotype — Height 28,7 mm., greatest diameter 16,0 mm.

Variability. — The concavity of the spire whorls is not constant. Voung postnuclear whorls have a keel somewhat projecting over the suture. Later the suture may be appressed to the keel or there may be a distance between them. It is observed in a single specimen that both situations may occur simultaneously, i.e. that the suture is appressed to the shoulder, then turns anteriorly for some distance, and finally rejoins the shoulder. Details of the spiral sculpture on the body whorl are considerably variable ⁽¹⁾.

Remarks. — The material consists of about 80 shells which are constant in general outline. Protoconchs and the margin of the outer lip are rarely preserved. Paratypes have been sent to the British Museinn (Natural History) , the Paleontological Research Institution, Ithaca, New York, and the U.S. National Museum, Washington, D.C. ⁽¹⁾

Comparisons. — C. imitator Brown and Pilsbry (1911, p. 342, pi. 23, fig. 4) from the Panama Canal Zone is a larger species with a slightly concave spire. Its first postnuclear whorls are tuberculate in contrast to C. talis. C. talis has no spiral threads on the spire whorls and is stouter than C. imitator s.str. C. imitator lins Woodring (1928, J). 209, pi. 10, figs. 5, (i) from Bowden, Jamaica, topotypes of which are at hand, mainly differs by its larger size. Young individuals of it have the whole surface of the body whorl spirally striated, whereas in C. talis this ornamentation always remains restricted to the lower part of the body whorl. C. talis tends to be stouter ⁽¹⁾.

C. floridatitis costaricensis Olsson (1922, p. 45, pi. 3, figs. 3, 9) from the Gatun formation of Costa Rica is larger and more slender than C. talis and shows spiral threads on the spire whorls. It closely resembles C. imitator, as stated by Olsson, and might prove to belong to that species. C. bocapanensis Spieker (1922, p. 38, pi. 1, fig. 3) from the lower Zorritos formation of Peru is also a larger and more slender species with a spiral ornamentation covering the whole body whorl, although weaker in its upper part ⁽¹⁾.

The spire whorls of C. vaughanensis Mansfield (1935, p. 20, pl. 1, fig. 8) from the Area Zone (upper middle Miocene) of Florida carry spiral threads. The holotype has nearly the double dimensions of the holotype of C. talis, an inconspicuous spiral sculpture around the siphonal canal, but otherwise similar proportions. C. chipolanus Dall (1896, p. 42) from the Chipola formation of Florida differs by its concave spire, the more conspicuous constriction above the siphonal canal, and in details of its spiral sculpture. A spire similar to that of C. talis has the Recent C. bermudensis lyniani Clench (1942, p. 35, pi. 13, fig. 3) from Florida. Further comparison is not possible with the help of the original description and figure alone ⁽¹⁾.

E’ una conchiglia piccola e robusta. La spira è moderatamente elevata, dal profilo nel complesso piatto; ogni singolo giro presenta comunque una considerevole concavità, variabile da spira a spira. La protoconchiglia è elevata ed è formata da tre giri lisci, gli ultimi due dei quali hanno pressoché il medesimo diametro. I giri postnucleari sono nove, nessuno dei quali presenta grani sulla spalla, talvolta bruscamente carenata. L’ornamentazione sopra la spalla è formata da linee di accrescimento ben evidenti, ma senza linee spirali. Il profilo dell’ultimo giro è quasi rettilineo, leggermente convesso nella parte superiore, più o meno concavo verso la base. La fasciola sifonale è talvolta rigonfia. L’ornamentazione spirale sulla parte inferiore dell’ultimo giro è formata da 10 – 14 scanalature di larghezza variabile, le più alte delle quali sono generalmente più piccole con ampi interspazi; queste sono seguite da scanalature più ampie, che rimpiccioliscono verso la base. I primi giri postnucleari possono mostrare una piccola carenatura, che può essere assente nei giri successivi ⁽¹⁾.

Distribuzione:


Conus talis⁽¹⁾ Plate 78 n. 8 - Paratype H 13825 mm. 23,0	Conus talis ⁽¹⁾ Holotype H 13824 28,7 x 16,0 mm.

Conus talis ⁽¹⁾ Left: Paratype H 13827 – Right : Paratype H 13826

Conus talis mm. 25,4