GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


secondary spiral present or absent in interspaces on base. Nodes on basal spirals long, low, and not well defined. Edge of umbilicus not sharply angulated and therefore junction of basal and columellar lips not angulated. Interspaces on base and umbilical wall adjoining innermost basal spiral roughened by axial wrinkles. Remainder of umbilical wall smooth, aside from subdued growth lines.
 Height (incomplete) 17.5 mm, diameter 19 mm (type). Height (almost complete) 18.7 mm, diameter 19 mm (paratype).
 Type: USNM 561311; paratype, Stanford Univ.
 Type locality: 155c (USGS 16915, Gatun Third Locks excavation, east side of excavation, 1 mile (1.6 km) north of Gatun Lake, Canal Zone), middle part of Gatun formation.
 This species is represented by two specimens, both collected at the Gatun Third Locks. It has a less angulated umbilical border than Calliostoma grabaui Maury (1917, p. 155, pl. 24, fig. 19), from the middle Miocene Gurabo formation of the Dominican Republic, and also has weaker nodes on the spirals of the body whorl, particularly on the base. C. mancinella Olsson (1922, p. 164, pl. 15, figs. 9, 10), from the middle Miocene of Costa Rica, has a lower spire, less inflated spire whorls, and more widely spaced basal nodes. The more inflated spire whorls and less angulated umbilical border of C. eremum differentiate it from the living 0. sayanum Dall (1889, p. 370, pl. 33, figs. 10, 11), which furthermore is twice as large. The two specimens of C. sayanum mentioned by Dall in 1889 still are the only representatives of that species in the collections of the U. S. National Museum: the type dredged at a depth of 120 fathoms 20 miles southeast of Cape Hatteras and a body-whorl fragment from a depth of 107 fathoms 36 miles south of Cape Hatteras.
 Occurrence: Middle part of Gatun formation (middle Miocene), eastern area, localities 155, 155c.
 Family TURBINIDAE
 Genus Turbo Linn6
Linn6, Systema naturae, ed. 10, p. 761, 1758. Type (logotype, Montfort, Conchologie syst6matique, v. 2,
 p. 203, 1810): Turbo petholatus (Turbo petholatus Linn6),
 Recent, tropical western Pacific and Indian Oceans.
 Subgenus Marmarostoma Swainson
Swainson, Zoological illustrations, 2d ser., v. 1, text accompanying pl. 14 (unnumbered), 1829.
Type (orthotype): Turbo chrysostomus Linn6, Recent, tropical
 western Pacific.
 When Swainson proposed the generic name Marmarostoma, he designated Turbo chrysostomus as the type. The only species of Marmarostoma, however, described by him at that time, M. undulata (correctly M. un-


dulatum), evidently is the Panamic species named, Turbo saxosus by Wood (1828, p. 20, pl. 6, fig. 45) a year earlier; that is, it is a species of the subgenus Callopoma Gray (Gray, M. E., 1850, p. 87; type (logotype, Cossmann, 1895-1924, pt. 11, p. 116, 1918):11 Turbo fluctuosus Wood, cited by Cossmann as Turbo fluctuatus Gray), Recent, tropical eastern Pacific),t characterized by a deep central pit and granular ribs on the operculum.
 Many years ago Iredale (1915, p. 444) discussed Swainson's type designation, but, apparently on th tacit assumption that Turbo marmoratus Linn6 is the type of Turbo, he considered Marmarostoma to be a, synonym of Turbo. Thiele in his Handbuch der svstematischen Weichtierkunde and Wenz in his treatise on fossil gastropods have called attention to the availability of Marmarostoma in place of the better known Senectus Swainson (1840, p. 348; type (logotype), Herrmannsen, 1846-52, v. 2, p. 438, 1848: Turbo chrys, ostomus Linn6, (cited by Swainson as "chrysostomus Mart."), which is an objective synonym.
 Caribbean fossil and Recent species that are referred to Afarmarostoma are not typical of that subgenus. The operculum of Turbo chrysostomus and its close allies has marginal oblique nairow grooves separating minutely granular bands, whereas the operculum of the Caribbean species has a more or less distinct shallow marginal ledge and is faintly granulai or smooth.
 Turbo (Marmarostoma) aff. T. castaneus Gmelin Plate 20, figure 10
 Of medium size, sculpture nonlamellar. Early whorls bearing a conspicuous practically smooth basal spiral. Later whorls weakly shouldered, sculptured with noded spirals. Somewhat worn operculum assumed to represent this species is smooth, bearing a poorly defined shallow marginal ledge.
 Height (not quite complete) 20.5 mm, diameters (incomplete) 18 mm (figured specimen). An incomplete apparently immature shell and asso-4 ciated operculum from the middle part of the Gatun formation and a mold of a few whorls from the Toro limestone member of the Chagres sandstone are identified as Turbo aff. T. castaneus. They may, in fact, represent the Recent Caribbean T. castanets. The operculum fitted into a shell considerably larger than the only shell collected at the same locality.
 The typical form of T. castaneus, as long accepted, is sculptured with nonlamellar noded spirals. Recent Caribbean shells that have noded spirals but also have thin lamellae forming vaulted scales on the primary spiral at the shoulder, or on that spiral and others, have been referred to T. crenulatus, also named by Gmelin. T. crenulatus has the same geographic range


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