GASTROPODS: TROCHIDAE TO TURRITELLIDAE


 Of medium size. Microscopic spiral lineation of f,'sh Recent shells not apparent, presumably due to slight wear. Umbilical rib narrow, slowly enlarging; unfilled umbilical space wide.
 Height (incomplete) 16 mm, diameter (incomplete) 34 mm (figured specimen).
 The Gatun formation yielded three incomplete fossils that closely resemble Recent shells of Neverita helicoides "of medium size. The largest fossil, if it were complete, would have a diameter of about 45 millimeters. The largest Recent shells of N. helicoides in the U. S. National Museum collections have a diameter of between 55 and 60 millimeters. Slightly worn Recent shells do not show the very fine slightly wavy micro-scopic lineation of fresh shells.
 Neverita nereidis Maury (1917, p. 137, pl. 23, figs. 17, 18), which occurs in the Cercado formation of the Dominican Republic, is closely allied to N. helicoides. Like the Gatun fossils, it is smaller than N. helicoides (diameter 35 mm). Moreover it has a wider umbilical rib than the Recent species. However remarkable it may be to recognize two very closely related species of Hypterita in the Miocene of the Caribbean region, the Gatun fossils are identified as N. helicoides on the basis of their narrow umbilical rib.
 The fragment from the Miocene of Banana River, Costa Rica, identified by Olsson as N. nereidis, is not accessible at the present time. A fragment from that area, however, in the collections of the U. S. National Museum has a narrow umbilical rib and is doubtfully identified as N. helicoides.
 Gray's name is far from satisfactory. He cited it as Barnes' manuscript name, a name that was still-born so far as Barnes' mention of it is concerned. Unfortunately the name, as Gray's name, is nomenclaturally available and therefore, as pointed out by Hertlein and Strong, replaces the well known name Neverita glauca.
 Occurrence: Lower and middle parts of Gatun formation (middle Miocene). Lower part, locality 136a. Middle part, eastern area, locality 155b; western area, 'locality 161c. Middle Miocene, eastern Costa Rica (identification doubtful). Pliocene, western Costa Rica. Recent, Magdalena Bay, Baja California, and Gulf of
-California to Perd.
 Subfamily SININAE
 Genus Sinum Rdding
 R6ding, Museum Boltenianui', pt. 2, p. 14, 1798. Type (logotype, Dall, U. S. Natl. Mus. Bull. 90, p. 109, 1915):
 Helix haliotoidea Linn6 (cited by R6ding as Helix halioloidea
 Gmelin), Recent, western Pacific(?).
 The collections from the Gatuncillo formation, the marine member of the Bohio(?) formation, and the
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Caimito and Culebra formations include unidentified species of Sinum, represented by poorly preserved specimens. The Culebra Sinum may be the species from the Anguilla formation, of the island of Anguilla, recorded as Sinum chipolanum (Dall) (Cooke, 1919, p. 124, pl. 5, figs. 6a, 6b), but the species so identified is smaller and more depressed than S. chipolanum.
 A species from the Gatun formation, Sinum gatunense (Toula) (1909, p. 697, pl. 28, figs. 3a, 3b, 3c) is not represented in the collections examined. It was compared by Toula with the Recent West Indian S. perspectivum (Say) and, according to his illustrations, is closely related to that species and the Recent Panamic S. noyesi Dall. Toula's species is greatly depressed and has a very narrow base. S. gatunense has been recognized in the Cercado formation of the Dominican Republic (Maury, 1917, p. 138, pl. 24, fig. 2) and in the Bowden formation of Jamaica (Woodring, 1928, p. 390, pl. 31, figs. 3, 4). S. dodonum Gardner (1926-47, p. 554, pl. 59, figs. 37, 39, 1947), of the Oak Grove sand member of the Shoal River formation of Florida, probably is a large form of S. gatunense. Though Toula's illustration shows no faint spirals on the base, some specimens of the species from the Dominican Republic and Jamaica identified as S. gatunense have faint basal spirals like those on the type of S. dodonum.
 Sinum euryhedra Woodring, n. sp.
 Plate 21, figures 4, 7, 10
Sinuan species, Woodring, Carnegie Inst. Washington Pub. 385, p. 390, 1928 (Miocene, Jamaica). Of medium size, moderately depressed, base relatively very wide. Protoconch consisting of about I1% smooth whorls. Spire whorls and body whorl between periphery and suture sculptured with spiral bands, separated by grooves that, for the most part, are of about same width as the bands, but near suture are twice as wide as the bands. Base smooth except for exaggerated growth lines. A narrow groove lies behind posterior part of everted columellar lip.
 Height (incomplete, spire crushed) 11 mm, diameter (incomplete) 27 mm (type).
 Type: USNM 561441.
 Type locality: 137a (Stanford University locality 2655, Transisthmian Highway, 1.7 kilometers northwest of Sabanita, Panamd; same as USGS 16911), lower part of Gatun formation.
 The type, an incomplete and somewhat crushed specimen collected from the lower part of the Gatun formation by T. F. Thompson, is the only representative of this species. It is characterized by moderate depression, wide base, and strong sculpture. Owing to crushing, the spire is too low in apertural aspect (pl. 21, fig. 4).


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