GASTROPODS: TROCHIDAE TO TURRITELLIDAE


which are not flangelike. The difference is particularly marked on the wide posterior primary, the posterior face of which is only slightly concave. On most of the specimens the posterior primary is doubled-on a few it is tripled. Though the primaries are strongly noded, i the nodes are not as conspicuous as on the typical form, possibly owing to slight wear.
 Mansfield's Turritella aff. T. perattenuata praecellens Pilsbry and Brown, of the early Miocene at Machapure (or Machapoorie) Quarry, Trinidad, has similar heavy strongly noded primaries.
 This unnamed subspecies of T. altilira is found in the middle member of the Caimito formation in the Gatun Lake area and in the Quebrancha limestone member of the Caimito in the Quebrancha syncline. The Quebrancha limestone fossils are poorly preserved. A mold of a small specimen from the Emperador limestone member of the Culebra formation evidently is more similar to the typical form, as intermediate whorls have high primaries.
 Occurrence: Middle member of Caimito formation (late Oligocene), Gatun Lake area, locality 56. Quebrancha limestone member of Caimito formation (late Oligocene), Quebrancha syncline, locality 62. Emperador limestone member of Culebra formation (early Miocene), Gaillard Cut, locality 120 (T. altifira s. 1.).

 Turritella (Torcula) altilira praecellens Pilsbry and Brown Plate 23, figures 2, 8
 Turritella perattenuata praecellens Pilsbry and Brown, Acad. Nat.
 Sci. Phila. Proc., v. 69, p. 36, footnote, pl. 5, fig. 12, 1917
 (Miocene, Dominican Republic).
 Of medium size, slender. Primary spirals relatively low, moderately or weakly noded. Posterior face of posterior primary slightly concave. Posterior primary wider than anterior, generally doubled. Minor spirals between primaries of subequal strength. Sculpture of early whorls like that of typical T. altilira, but minor spirals appearing several whorls later. Growth line like that of typical T. altilira.
 Height (incomplete, 8 whorls) 42 mm, diameter 12.5 mm (larger figured specimen). Height (incomplete, 4+ whorls) 30.5 mm, diameter 13 mm (smaller figured specimen).
 Type: Acad. Nat. Sci. Phila. 2608.
 Type locality: Dominican Republic, Miocene (presumably Baitoa formation, late early Miocene).
 This form of Turritella altilira, like the subspecies in the Caimito formation, lacks flangelike primary spirals. It is more slender than the Caimito subspecies and its primaries are not as strongly noded. Suppression of the nodes at a diameter of 12 millimeters suggests that it does not reach a large size.


 The fossils from Panami may represent a local race of T. altilira not of the same genetic stock as T. altilira praecellens. Nevertheless the identification emphasizes the direction of differentiation from the typical form. Collections of T. altilira praecellens from the Baitoa formation of the Dominican Republic include larger specimens than those from Panami and some that have more strongly noded primaries. Though T. altilira praecellens was described as a subspecies of T. perattenuata Heilprin, of the Pliocene of Florida, it apparently lacks the greatly attenuated whorls of that species and evidently is more closely related to T. altilira. T. perattenuata, however, also is a nonflanged member of the T. altilira group.
 T. montserratensis (Mansfield, 1925, p. 53, pl. 9, figs. 5, 6), which occurs in the Telemaque sand member of the Springvale formation (late Miocene) of Trinidad and should be assigned subspecific rank under T. altilira, is very similar, but its posterior spiral is not doubled.
 The form of T. altilira identified as T. altilira praccellens occurs in the lower part of the Gatun formation. It is, indeed, the only altilira-like Turritella in the U. S. National Museum collections from that part of the formation. A form comparable to T. altilira praecellens, but very weakly noded and less slender, is found in the middle part of the Gatun at locality 144. The lower Gatun subspecies (or variety) and the typical T. altilira are represented in Hill's Gatun collection labelled Vamos Vamos (locality 158).
 Occurrence: Lower and middle parts of Gatun formation (middle Miocene). Lower part, localities 136a, 137, 138, 138a. Middle part, eastern area, localities 144 (T. altilira subsp., cf. T. altilira praecellens), 158. Baitoa formation (late early Miocene), Dominican Republic.
 Subgenus? (Merriam's T. ocoyana stock)
 Turritella ef. T. subgrundifera Dall Plate 16, figure 3
 Small, slender, strongly carinate at about anterior fourth of whorl. Sculpture consisting of 6 or 7 widely spaced spirals. Spiral immediately in front of and behind carina-forming spiral and 1 or 2 near posterior suture weaker than others. Sculpture of early whorls and growth line not known.
 Height (incomplete, 3 whorls) 18 mm, diameter 5 mm (figured specimen). Height (incomplete, 3 whorls) 25 mm, diameter 15 mm (increased by crushing).
 The whorl profile, slender outline, and widely spaced spirals of this species, represented by two poorly preserved fragments from the Culebra formation, strongly suggest Turritella subgrundifera, of the Chipola formation of Florida (Gardner, 1926-47, p. 590, pl. 57, fig. 1,


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