GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


147h, 151, 152, 155, 155a, 155b, 155c, 159, 160 (Crucibulum cf. C. springvaleense); western area, locality 162a. Upper part, western area, locality 185. Springvale formation (late Miocene), Trinidad. Miocene, Bolivar, Colombia.
 Family NATICIDAE
 Subfamily NATICINAE
 Genus Natica Scopoli
Scopoli, Introductio ad historiam naturalem, p. 392, 1777. Type (logotype, Harris, Catalogue of Tertiary Mollusca in the
 British Museum; pt. 1, Australasian, p. 255, 1897); Nerita
 vitellus Linn6, Recent, tropical western Pacific.
 Anton (1839, p. 31) also designated Nerita vitellus as the type of Natica at a much earlier date than Harris. Anton's designation, however, is of doubtful validity, as it is a designation for Natica Lamarck.
 Subgenus Natica s. s.?
 Natica (Natica?) species
 The collections from the marine member of the Bohio(?) formation at Vamos Vamos include two naticid opercula that have a narrow marginal rib, separated by a shallow groove from a wider second rib. They represent Aatica s. s. or possibly some other subgenus that has a similar operculum. The larger specimen has a restored length of about 12 millimeters and a width of 7.5 millimeters. Small poorly preserved shells from locality 42 may represent this species.
 Occurrence: Marine member of Bohio(?) formation (late Eocene or early Oligocene), localities 40, 40d, 42 (identification doubtful).
 Natica (Natica?) bolus Brown and Pilsbry Plate 20, figures 1-3
Natica bolus Brown and Pilsbry, Acad. Nat. Sci. Phila. Proc., v. 64, p. 508, pl. 22, fig. 9, 1913 (Miocene, Canal Zone). Natica young Maury, Bull. Am. Paleontology, v. 5, no. 29, p. 135, pl. 23, figs. 11, 12, 1917 (Miocene, Dominican Republic). Pilsbry, Acad. Nat. Sci. Phila. Proc., v. 73, p. 386, pl. 34, fig. 21, 1922 (Miocene, Dominican Republic). Maury, Bull. Am. Paleontology, v. 10, no. 42, p. 239, pl. 40, fig. 4, 1925 (Miocene, Trinidad). Mansfield, U. S. Natl. Mus. Proc., v. 66, art. 22, p. 57, 1925 (Miocene, Trinidad). Natica finitima Pilsbry and Johnson, Acad. Nat. Sci. Phila. Proc., v. 69, p. 173, 1917 (Miocene, Dominican Republic). Not Natica youngi Maury, Li, Geol. Soc. China Bull., v. 3, p. 266, pl. 6, figs. 47, 47a, 1930 (Miocene, Panama Bay; Natica unifasciata Lamarck, fide Pilsbry, Acad. Nat. Sci. Phila. Proc., v. 83, p. 432, 1931, Recent, PanamA Bay). Not Natica (Polinices) cf. youngi Maury, Trechmann, Geol. Mag., v. 72, p. 550, pl. 20, figs. 3-5, 1935 (Miocene, Carriacou); Polinices sp.
 Of medium size, thick-shelled, spire very low or moderately low, shoulder strongly or slightly inflated. Protoconch not clearly differentiated from remainder of shell, apical whorl large. Umbilicus wide, umbilical rib


narrow, ending in a small callus lobe bearing a shallow anterior depression. A narrow deep groove lies in front' of umbilical rib and callus pad, separating them froui umbilical border. Parietal callus thick, especially in front of junction with outer lip, where it forms a ridge. On immature shells anterior part of parietal callus relatively wider than on mature shells and roofing over posterior end of umbilicus as it extends forward to join-' umbilical lobe. Operculum assumed to represent this species bearing a narrow marginal rib, separated by a narrow groove from a second rib that is as narrow as the marginal rib or slightly wider.
 Height 14.5 mm, diameter 15.2 mm (figured mature specimen). Height 9.7 mm, diameter 10.2 mm (figured immature specimen).
 Type: Acad. Nat. Sci. Phila. 3846.
 Type locality: Gatun Locks excavation, Canal Zone, middle part of Gatun formation.
 The type, the largest of 6 in the type lot, is a small immature shell (height 9 millimeters). On the type and~ other immature shells, such as that shown on plate 20, figure 3, the anterior part of the parietal callus is wide and roofs over the posterior end of the umbilicus. On mature shells more of the umbilicus is uncovered. The. largest shell, which is incomplete, has a height of 19.5 millimeters. Very low-spired shells have an inflated shoulder, whereas shells that Pave a higher spire have a less inflated shoulder. Two small opercula assumed to represent N. bolus were found in association with shells at locality 155c and another of medium size at locality 172.
 Though Natica bolus is fairly widespread in the Gatun formation, only a few specimens were collected at any, locality, except locality 177b. N. youngi, from the Miocene of the Dominican Republic, reaches a somewhat larger size (height 24 millimeters), but has the umbilical and callus features, as well as the outline, of N. bolus. N. youngi from the Miocene of Trinidad has a narrower umbilicus and less conspicuous umbilical rib than N. bolus, but is considered conspecific. N. young cocleana Olsson (1922, p. 155, pl. 13, fig. 8; Miocene,, Costa Rica), however, has a narrow umbilicus, weak umbilical rib, and narrower umbilical callus lobe, and evidently is not closely related. An early Miocene species from Costa Rica, N. milleri Gabb (1881, p. 338, pl. 44, fig. 3) has a higher spire and weaker umbilical rib. N. castrenoides Woodring (1928, p. 377, pl. 30, fig. 5;1 Miocene, Jamaica) and its Recent Caribbean analog,i N. castrensis Dall (1889, p. 293), have a wider and weaker umbilical rib and thinner parietal callus. N.J bolus appears to have no close living allies in either, Caribbean or Panamic waters.
 The strong, though narrow, umbilical rib indicates that N. bolus is not closely related to N. vitellus; it


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