GASTROPODS: TROCHIDAE TO TURRITELLIDAE


relatively flat-whorled and have strong primaries (pl. 23, fig. 14). Strong minor spirals are less common in the lower part of the formation than in the middle part. Specimens that have axial waves were not found in the lower part and are not common in the middle part, except at localities where the subspecies (or variety), described under the next heading was collected. Some specimens in the collection from locality 150a, which is close to, if not at, the type locality, have weak axial waves.
 The profile, sculpture, and growth line of late whorls indicate that the typical form, or closely related forms, occur in the Miocene of northwestern PanamA, Costa Rica, Colombia, Ecuador, and Venezuela. Confirmation, based on the sculpture of the early whorls, is desirable. Weisbord's T. cf. T. gatunensis, from the Miocene of Colombia, may be referred to the typical form, despite its wide primaries. The early sculptured whorls of T. gatunensis caronensis Mansfield (1925, p. 51, pl. 8, figs. 12-14), of the Miocene of Trinidad, are not attenuated; the first few sculptured whorls are weakly carinate; and later early whorls are not as strongly carinate as those of T. gatunensis. This Trinidad species of Turritella is closely related to T. gatunensis, but presumably is to be given specific rank.
 There seem to be no close relatives of T. gatunensis in the Miocene of southeastern United States. Though intermediate and late whorls of T. gatunensis ifountensis Mansfield (1935, p. 41, pl. 4, figs. 1, 2), from deposits of middle Miocene age in western Florida, are practically indistinguishable in sculpture and growth line from specimens of T. galunensis that have a strong posterior minor spiral, they enlarge less rapidly. The earliest preserved whorls (not quite the earliest sculptured whorls) are not carinate and are sculptured with 6 or 7 spirals. T. blountensis therefore is not a subspecies of T. gatunensis. The small specimens from the Shoal River formation of Florida doubtfully recorded as T. gatunensis blountensis (Gardner, 192647, p. 592, pl. 57, figs. 11, 12, 1947) are less like T. gatunensis in whorl profile. The earliest preserved whorls are not carinate and are sculptured with three strong spirals.
 Mansfield's T. gatunensis, from the late Oligocene of Florida, has the sculptural pattern of that species, but late whorls are more or less uniformly convex. The earliest preserved whorls have two spirals. One specimen shows a suggestion of a moderately deep growthline sinus, with the apex a little behind the middle of the whorl, and a narrow growth-line angle. This species of Turritella is without much doubt related to the species from Vamos Vamos, T. adela: the species mentioned by Mansfield as T. gatunensis, following Dall's identification. According to Mansfield, a form


of T. gatunensis from the "lower faunal zone" of the Gatun formation has early whorls like those of the species of Turritella from Vamos Vamos. That observation, however, evidently was based on some misunderstanding, for no specimen of T. gatunensis from the Gatun formation that shows the early whorls has such sculpture. The affinities of Mansfield's (1940, p. 218, pl. 27, figs. 56, 57) Turritella cf. T. gatunensis, from the late Oligocene Chickasawhay marl, are uncertain. The growth line is unknown and the early whorls of the only specimen that shows them are too poorly preserved to reveal the sculpture.
 Occurrence: Calcareous sandstone member of Caimito formation (early Miocene), Madden basin, locality 82 (mold, identification doubtful). Lower, middle, and upper parts of Gatun formation (middle Miocene). Lower part, localities 136a, 137, 137a, 138, 138a. Middle part, eastern area, localities 140, 141, 144, 144a (identification doubtful), 147a, 147d, 147e, 1471, 150a, 153, 155, 155b, 155c, 156, 157, 158, 159, 159a, 159b, 160; western area, localities 161, 161a, 169. Upper part, eastern area, localities 163, 172. Toro limestone member of Chagres sandstone (early Pliocene; molds, identification doubtful), localities 194, 196. Late Miocene, Water Cay, Panama. Middle Miocene, Costa Rica. Middle Miocene, Bolivar, Colombia. Miocene, Falcon, Venezuela. Subibaja formation (early Miocene) and Progreso formation (middle Miocene), Ecuador.
 Turritella gatunensis rhytodes Woodring, n. subsp.
 Plate 23, figures 10, 11, 17
 Moderately large, slender. Protoconch and early whorls like those of typical form. Posterior part of intermediate and late whorls strongly constricted. On intermediate whorls minor spirals, particularly one or more between primaries, increase in strength until on late intermediate and late whorls they are as strong as primaries, the whorls losing the typical T. gatunensis profile. Spirals of intermediate whorls more or less undulated by axial waves on most specimens. Growth line like that of typical form.
 Height (incomplete) 66 mm, diameter 16.5 mm (type).
 Type: USNM 561395; paratypes, Stanford Univ.
 Type locality: 162a (USGS 8359, lower trail on west side of Rio Chagres northwest of Gatun Dam, Canal Zone), middle part of Gatun formation.
 Turritella gatunensis rhytodes is abundant in the middle part of the Gatun formation at localities 162 and 162a on the west side of Rio Chagres northwest of Gatun Dam. Presumably it is a local subspecies or variety. The typical form occurs in the middle part of the Gatun at nearby localities, but is not represented


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