GASTROPODS: TROCHIDAE TO TURRITELLIDAE


Type (logotype, Reheder, Biol. Soc. Washington Proe., v. 56,
 p. 41, 1943): Trochila spiralis Schumacher (=Trochus radians Lamarck= Turbo trochiforios Born), Recent, Ecuador to
 Chile.
 Trochita has a thick shell, distinct suture, and moderately strong to strong radial sculpture. The free edge of the platform is convex forward, except at the distal margin, where it bears a narrow identation. The ':columellar edge of the platform is reflected only at its insertion. On adult shells this short reflected border is molded on the platform, like callus. The genus and its species were discussed by Rehder (1943) in the publication cited for the type designation.
 Trochita heretofore has not been recorded from the Caribbean region. It is now extinct there, and in the western Atlantic is limited to the Falkland Islands and the coast of Argentina. Though it occurs in the Miocene and Pliocene of California, in the eastern Pacific it is i now found only south of the equator. The survival of the genus in west African waters-a genus otherwise confined to the Peruvian, Magellanic, and South African provinces-is nore readily understood in view of its occurrence in the Miocene of the Caribbean region and in the Pliocene and Pleistocene of west Africa. The West African species is considered conspecific with the Miocene Caribbean fossil and the Recent eastern Pacific species. It is an expectable fossil in the West African Miocene.
 Trochita trochiformis (Born)
 Plate 19, figures 11-14
 Turbo trochiforis Born, Index Musei Caesarei Vindobonensis'
 p. 355, 1778 (sole citation: Knorr, pt. 3, pl. 29, figs. 1, 2, 1768,
 "Antillean Islands").
 Trochus radians Lamarck, Encyclop6die mthodique, Histoire
 naturelle des vers, t. 3, pl. 445, figs. 3a, b; Liste, p. 10, 1816.
 Lamarck, Histoire naturelle des aniaux sans vertlbres, t. 7,
 p. 11, 1822 (Recent, mer des Antilles").
 Calyptraca (Trochatella) trochifornis (Gmelin), d'Orbigny, Voyage dans 1'Amdrique Muridionale, t. 5, pt. 3, 1c. 461, pl. 59, fig. 3, 1841 (Recent, Chile, Perd; Calyptraea radians in explanation of plate). Nickles, Manuels Ouest-Africains, t. 2, p. 73, fig. 99, 1950 (Recent, Angola). Lecointre, Morocco Service Gtologique, Notes et 6m. 99, t. 2, p. 108, pl. 25, figs. 1-4,
 1952 (Pleistocene, MIorocco).
 Infndibulu trochiforcce (Gicelin), d'Orbigny, Voyage dans
 l'Anirique M6ridionale, t. 3, pt. 4 (Paltontologie), p. 158,
 1842 (Pleistocene, Chile).
 Trochila radians (Lamarck), Reeve, Conchologia Iconica, v. 11,
 Trochita, pl. 1, species 3, 1859 (Recent, Chile). Sowerby, Thesaurus Conchyliorum, v. 5, p. 64, pl. 451, figs. 95, 96, 99, 1883 (ltecent, Chile). Relider, Biol. Soc. Washington Proc.
 v. 56, p. 42, 1943 (Recent, Ecuador to Chile); see this publication for other citations and synonymy.
 Calyptraea (Trochita) trochiforsits (Gmelin), Grant and Gale,
 San Diego Soc. Natural History Mem., v. 1, p. 795, pl. 31, fig. 11, 1931 (Miocene and Pliocene, California; RecentPanamil to Perd).


Trochatella trochiformis (Gmelin), Lecointre, Jour. Conchyliologie, t. 90, p. 240, unnumbered pl., fig. 2, 1950 (Pliocene,
 Pleistocene, Morocco).
 Of medium size, moderately low spired or moderately high spired, apex broken. Sculpture consisting of heavy crude axial ribs. Platform broken back to insertion.
 Maximtuim diameter 28.8 mm, height (incomplete) 10.7 mm (smaller figured specimceen). Maximum diameter 43.5 ncm, height (almost complete) 27 mm (larger figured specimen).
 This calyptraeid is represented by two specimens from the lower part of the Gatun formation, both collected by T. F. Thompson. Though the interior of the larger specimaen is inaccessible and the platform of the smaller is broken far back, they are identified with considerable confidence as Trochita trochijormis. The middle part of the Gatun formation in the western area at locality 151 yielded a wor thicek-shelled apical fragment listed as Trochita? sp. Incomplete and poorly preserved fossils from the middle member of the Caimito formation in the Gatun Lake area and the Culebra formation suggest that the lineage of T. trochiformis can be traced back to the late Oligocene. None of these Caimito and Culebra fossils, however, is unequivocally identified.
 Trochita trochijormis now ranges from 'Manta, Ecuador, to Valparaiso, Chile. It is low spired to high spired. On low-spired shells the platform is almost flush with the base of the shell; on high-spired shells it is a considerable distance above the base. The heavy crude axial ribs are characteristic. The largest Recent specimen i the collection of the U. S. National Museum has a maximum diameter of 65 millimeters.
 A small form of Trochita trochiformis (recorded as T. radians) occurs in formations of Pliocene age i California as far north as the Santa Maria district (Arnold aced Anderson, 1907, p. 60, pl. 21, fig. 1; Woodring and Bramlette, 1950 [1951], p. 72, pl. 13, fig. 19), in Santa Barbara County. Early and middle Xciocene forms from California have been identified as Trochita costellata Conrad (Eldridge and Arnold, 1907, p. 148, pl. 32, fio-. 3; Locl and Corey, 1932, p. 268, pl. 63, fig. 11), and late Miocecce forms have been named "Calyptraca" diabloensis Clark (1915, p. 485, pl. 70, fig. 9) and "Calyptraea" ioartini Clark (1915, p. 486, pl. 70, fig. 8). As suggested by Grant and Gale, these heavily ribbed Miocene forms, ranging in age from early to late Miocene, are probably to be referred to Trochita trochiformis. The inadequate type material of Trochita costellata Conrad (1857b, p. 195, pl. 7, fig. 3) consists of two molds showing traces of relatively fine ribs. Additional specimens from the type locality (Gaviota Pass in the western Santa Ynez Moiuntains, Santa Barbara


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