Conasprelloides multiliratus multiliratus (Bose, 1906)

Conasprelloides multiliratus walli  (Mansfield, 1925)

Conasprelloides multiliratus gaza  (Johnson & Pilsbry, 1911)

Conasprelloides multiliratus spiekeri  (Olsson, 1932)

Concha pequeña, forma de huso, componiéndose de 10 vueltas y un núcleo de 2 (?) vueltas. La espira es elegantemente cónica, sin adorno espiral pero con numerosas estrías finas de crecimiento; la quilla es lisa, la sutura muy distinta, casi canaliculada. La última vuelta está cubierta con numerosas (20) costillas espirales arredondadas, separadas por surcos más angostos. La abertura es larga y angosta; el labro es delgado, encorvado hacia adelante, el seno profundo y arqueado ⁽²⁾. 

Dimensiones: 

I    mm. 28,5 x 15,5

II   mm. 25,0 x 12,5

III  mm. 20,0 x 10,5

Nuestra especie corresponde bastante bien á los individuos jóvenes del tipo, pero se distingue de los ejemplares adultos principalmente por los surcos en la última vuelta; mientras que C. agassizi está surcado sólo en la parte anterior de la última vuelta, ésta está en nuestra variedad completamente cubierta por los surcos. En la fig. 8^a de Dall parece ser indicado que la quilla tiene incisiones, pero eu la descripción el autor no dice nada sobre esto, sino menciona solamente mauclias de color pardo rojizo. Como no hay diferencias más grandes que éstas creo que debemos considerar nuestra forma sólo como una variedad fósil de C. agassizi, Dall. Este fué encontrado hasta ahora solamente vivo eu el Golfo de México y á una profundidad entre 10 y 115 brazas. Nuestra forma parece pertenecer el grupo de los Conus surcados de las Antillas como C. planiliratus, Sowerby, y C. gracilissimus Guppy, pero se distingue del primero por la espira más alta y las costillas más i'edondas, del segundo por la figura más ancha, más robusta y por la espira más deprimida y lisa ⁽²⁾. 

Más se acerca á nuestra especie todavía Conus Burckhardti mihi que se distingue por la espira más alta y más esbelta, por la forma más larga, las costillas planas y los tubérculos que se encuentran en el margen de estas costillas en la parte anterior de la última vuelta.

Algo se asemeja Conus cruzianus, Dall, " del Terciario (Plioceno) de laisla de Santa Cruz en las Indias Occidentales, pero se distingue luego por su espira más baja con vueltas convexas ⁽²⁾. 

Dall compara su C. agassizi con C. peali, Green y C. pygmaeus Reeve creyendo primero que fuera una forma de transición que reúna las dos especies; pero no tenía más que un ejemplar joven. La mayor parte de los Conus surcados citados se conocen del Oligocenode las Antillas, el Conus burkhardti se encuentra en el Plioceno de Tuxtepec; éste y la variedad aquí descrita forman la transición al tipo de C. agassizi, Dall. 

C. agassizi var. multiliratus no es muy raro en Tuxtepec, he encontrado tres ejemplares casi completos, y varios más que están menos bien conservados ⁽²⁾.

Description:

Small, biconical, wide at shoulder, shoulder strongly carinate. Spire high, its profile almost smoothly conical. Protoconch slender, cylindrical, 2 ½ - to 3-whorled. Earliest part of first post-protoconch whorl bearing three to five axial riblets, followed by appearance of carinate shoulder, tuberculate on about first three whorls. Except on earliest whorls, succeeding whorl overlapping almost to carina. Anal fascicle slightly concave, bearing growth threads exaggerated at fairly regular intervals. Entire body whorl sculptured with strong, narrow, straplike spiral cords. On unworn shells exaggerated axial growth threads conspicuous in channels between cords, weaker or absent on cords themselves. Cords of immature shells rarely bearing low tubercles. Height (almost complete) 27,2 mm, diameter 14,4 mm (figured specimen) ⁽³⁾.

Type: Apparently lost, but may eventually be found at the Instituto de Geologia, Universidad Nacional de Mexico ⁽³⁾.

Type locality: Tuxtepec, Oaxaca, Mexico, Miocene ⁽³⁾.

• Though this strongly sculptured cone occurs in the three divisions of the Gatun formation but not in the upper part in the western area more than one or two specimens were collected at only two localities: nine at locality 138c and 10 at locality 139c. It is characterized by its broad-shouldered, biconical outline, and exaggerated growth threads on the anal fascicle and in the channels between the straplike spiral cords. The protoconch and spire whorls are like those of Conus imitator imitator, except that spiral threads are not discernible on the anal fascicle. One immature shell (height 17.8 mm, locality 138c) shows low tubercles on the spiral cords ⁽³⁾.

• Contrary to the view that was adopted in 1928, C. gaza is treated as a synonym of C. multiliratus multiliratus. Though no specimens of the nominate subspecies are available, Bose's illustrations show the essential features of C. gaza ⁽³⁾.

• C. multiliratus multiliratus is recognized in middle Miocene formations in the Tehuantepec area, Panama, northeastern and southwestern Columbia, Jamaica, the Dominican Republic, and possibly in Ecuador, and in deposits of late Miocene age in northwestern Panama. A comparable form of the species, perhaps the same as that in Ecuador, occurs in the middle Miocene of the Darien area. It lacks strong growth threads between the spiral cords, but the absence of that feature may be a matter of preservation and perhaps should not be overemphasized ⁽³⁾.

•  C. multiliratus walli Mansfield (1925, p. 13, pi. 2, figs. 1, 9; middle Miocene part of Brasso formation) may be recognized as a Trinidad race that is not as broadshouldered as the nominate subspecies. The type, which is somewhat worn, and the other shells in the type lot show scattered low tubercles on the spiral cords and slight undulations on the shoulder carina of the body whorl.

•  Spieker's two specimens from the Zorritos formation of Peru, identified as C. multiliratus gaza, are no longer available. When they were examined many years ago they were found to have weaker spiral cords and less distinct growth threads than C. multiliratus multiliratus ⁽³⁾.

•  C. multiliratus spiekeri Olsson (1932, p. 153, pi. 16, figs. 5, 7), also from the Zorritos formation, is sculptured with heavy tuberculate spiral cords and may be given specific rank ⁽³⁾.

•  C. turbinopsis Gardner (1926-47, p. 361, pi. 43, fig. 12, 1938; Shoal Eiver formation, Florida) has a turbinate outline and less conspicuous growth threads between the spiral cords. It has been identified in the Tehuantepec area (Perrilliat Montoya, 1960, p. 27, pi. 4, figs. 5, 6) ⁽³⁾.

•  C. clarki Kehder and Abbott (1951, p. 22, fig. 6), dredged off Louisiana at a depth of 29 fathoms, is sculptured with exaggerated growth threads on the anal fascicle and between the spiral cords. Its outline, however, is turbinate and the shoulder of all the postprotoconch whorls is tuberculate ⁽³⁾.

•  C. frisbeyce Clench and Pulley (Clench, 1953, p. 369, pi. 184, fig. 1; Campeche Banks, Yucatan) evidently is C. clarki ⁽³⁾.

Occurrence: Lower, middle, and upper parts of Gatun formation (middle Miocene). Lower part, localities 138c, 138d. Middle part, eastern area, localities 139c, 139e, 151, 159d. Upper part, eastern area, localities 173, 175, 176, 176a. Middle Miocene deposits, Tehuantepec area, Mexico, northeastern and southwestern Columbia. Bowden formation (middle Miocene), Jamaica. Cercado and Gurabo formations (middle Miocene). Dominican Kepublic. Limon formation (late Miocene), Bocas del Toro area, Panama ⁽³⁾.

Coloration pattern ⁽¹⁾

Probably two noninteracting patterns present. The primary (base) pattern consists of two continuous spiral bands, one at the base of the shell and one near the midpoint of the last whorl; these are lightly pigmented. The secondary pattern (which requires confirmation in specimens with better preserved patterns) seems to consist of spiral rows of dashes associated with the ribs that cover the last whorl. The two patterns differ slightly in the color of emitted light. Sutural ramp with lightly pigmented radial blotches.