GASTROPODS: TROCHIDAE TO TURRITELLIDAE


 Type locality: Gatun Locks excavation, Canal Zone, middle part of Gatun formation.
 Turritella mimetes is widespread in the middle parc of the Gatun formation, fairly common in the upper part in the western area, and probably occurs in the Toro limestone member of the Chagres sandstone. The whorl profile, determined by clasping of the succeeding whorl, and the sculpture are variable. The shells from the upper part of the Gatun, all collected in the western area, are relatively small. Their early whorls are not preserved, but their early intermediate whorls are like those of specimens from the middle part of the formation.
 T. mimetes is related to the Recent Caribbean T. variegate (LinnS). In fact, the marked similarity of late whorls in profile, sculpture, and growth line suggests that it is a subspecies of T. variegata. The early and early intermediate whorls of T. variegata, however, are medially carinate and rapidly enlarging. Allies of T. variegate are widespread in the Miocene of the CaribK bean region. It is not known whether any of them are closely related to T. mimetes. T. lloydsmithi Pilsbry and Brown (1917, p. 35, pl. 5, fig. 11), a middle and late(?) Miocene Colombian species, has more crowded spirals separated by very narrow grooves. Its early intermediate whorls are medially carinate and rapidly enlarging. It therefore is a close ally of T. variegata, possibly a subspecies. T. planigyrata Guppy (Mansfield, 1925, p. 55, pl. 9, figs. 1, 9; Rutsch, 1942, p. 131, pl. 8, fig. 5), the first of these Miocene Caribbean allies of T. variegate to be named, was based on fossils from the late Miocene Springvale formation of Trinidad. Its medially carinate and rapidly enlarging early intermediate whorls link it closely with T. variegate. Its 'sculpture is uniformly fine like that of some specimens of T. variegata.
 T. mimetes is also related to the Recent Panamic T. leucostoma Valenciennes, as identified by Kiener. The Recent species has attenuated early whorls, which, however, are medially carinate and have fewer spirals.
 Occurrence: Middle and upper parts of Gatun formation (middle and late Miocene). Middle part, eastern area, localities 141 (identification doubtful), 150, 154 (identification doubtful), 155, 155a, 155b, 157, 159; western area, localities 161, 161b, 161c, 162, 165 (identification doubtful), 170. Upper part, western area, localities 182, 182a, 183, 184, 185. Toro limestone member of Chagres sandstone (early Pliocene), locality 196 (identification doubtful).
 Turritella bifastigata Nelson
 Plate 22, figure 10
 Turritella bifastigata Nelson, Conn. Acad. Arts Sci. Trans., v. 2)
 p. 189, 1870 (Miocene, Perd). Spieker, Johns Hopkins Univ.
 Studies in Geology no. 3, p. 63, pl. 3, fig. 1, 1922 (Miocene,


 Perd). Hodson, Bull. Am. Paleontology, v. 11, no. 45, p. 48, pl. 30, fig. 1, 1926 (Miocene, Perd). Olsson, idem, v. 19, no. 68, p. 198, 1932 (Miocene, Peru).
Turritella gothica Grzybowski, Neues Jahrb., Beilage-Band 12, p. 645, pl. 20, fig. 10, 1899 (Mliocene, Perd). Woods, in Bosworth, Geology of the Tertiary and Quaternary periods in the north-west part of Peru, p. 110, 1922 (Miocene, Perd). Moderately large. Intermediate whorls rapidly enlarging; late whorls slowly enlarging. Last whorl or two loosely clasping. Early intermediate whorls medially carinate; late intermediate whorls slightly convex; late whorls slightly concave between a faint collar adjoining posterior suture and a more distinct, but narrower, collar adjoining anterior suture. Anterior collar forming a carina on whorls preceded by a loosely clasping whorl and on body whorl. Sculpture of early whorls not known. Early htermediate whohs sculptured with three subequal primary spirals (a median spiral forming a carina, a spiral adjoining anterior suture, and another halfway between them) and minor spirals. Anterior spiral developing into anterior collar, the other two gradually weaken. Late whorls sculptured with faint minor and microscopic spirals, the strongest of which corresponds to the second (from anterior suture) primary of intermediate whorls. Base sculptured with low wide spirals, between which and on which are fine minor spirals. Growth-line sinus moderately deep, the apex at middle of whorl; growthline angle wide.
 Height (not quite complete) 66 mm, diameter 18.5 mm (figured specimen).
 Lectotype: Peabody Museum, Yale Univ. 534.
 Type locality: Zorritos, Peru', Zorritos formation, late early Miocene.
 Late whorls are characterized by the sutural collars, producing a slightly concave profile, and faint spiral sculpture between the collars.
 Several names have been proposed for Miocene Caribbean allies of Turritella bifastigata, all of which probably are to be assigned subspecific rank under that species or the Recent T. broderipiana. The Colombian T. cartagenensis Pilsbry and Brown (1917, p. 34, pl. 5, fig. 13; Weisbord, 1929, p. 30, pl. 9, figs. 1, 2) has stronger spirals. The Costa Rican T. oreodoxa Olsson (1922, p. 152, pl. 14, fig. 1) has a wide posterior collar, no anterior collar, and stronger spirals. Hodson (1926, pp. 48-50, pl. 29, fig. 3, pl. 30, figs. 2-6) described fossils from the Miocene of Falc6n, Venezuela, as T. bifastigata maracaibensis and T. bifastigata democraciana. They are recorded together at numerous localities and evidently represent a variable form that probably is to be identified as T. bifastigata cartagenensis which also is recorded from the Miocene of Trinidad (Maury, 1925, p. 233, pl. 42, fig. 13).


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