GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


part of the formation in the eastern area. Eighteen of the 21 lots, however, consist only of immature specimens, up to a maximum of 115 immature shells in one lot. The largest shells are imperfect. A shell of medium size from locality 177c has an operculum in place (pl. 20, fig. 6). An incomplete operculum of medium size, not associated with shells, was found at locality 161. A small incomplete operculum, collected at locality 162, has three ribs, an indeterminate number of other lower ribs being covered with a glaze of enamel. The identification of this operculum is uncertain. The axial grooves disappear on the body whorl of an incomplete doubtfully identified shell from locality 147h.
 Though Brown and Pilsbry (1913, p. 508) recorded N. canrena from the Gatun formation and though Olsson (1922, p. 155, pl. 13, fig. 9) figured a specimen of that Recent Caribbean species from the Gatun formation near Gatun, that species is not represented in the Gatun collections of the U. S. National Museum or Stanford University. N. stenopa is of meduim size and has a high spire, small apical whorl, closely spaced axial grooves, and 5 or 6 ribs on the operculum. N. canrena, on the contrary, is much larger and has more inflated and more rapidly enlarging whorls, low spire, large apical whorl, more widely spaced axial grooves, more rapidly enlarging umbilical rib and correspondingly larger umbilical callus lobe, and 8 or 9 ribs on the operculum.
 On the basis of shell characters N. stenopa is closely related to a Recent Panamic species identified by Dall as N. limacina Jousseaume (1874, p. 14, pl. 2, figs. 7, 8). Jousseaume's description and illustrations suggest that the identification is erroneous. The operculum of N. limacina is unknown and the type locality is indefinite: "West Indies(?)". Dall's N. limacina is represented in the collections of the U. S. National Museum by one shell dredged in PanamS Bay at a depth of 33 fathoms. N. stenopa has a somewhat thinner shell, narrower groove in front of the umbilical rib and umbilical callus lobe, and wider umbilical opening back of the umbilical rib. Naticarius opercula, having 7 to 9 ribs, are represented by 2 lots from Panamai Bay, and also by lots dredged in the Gulf of California off Guaymas and La Paz, but it is not known that the opercula are to be associated with Dall's N. limacina. They agree with the operculum of N. colima Strong and Hertlein (1937, p. 174, pl. 35, figs. 12, 13, 16), dredged near Manzanillo, Mexico. N. colima, however, is thin shelled and has a very narrow umbilical rib and small umbilical callus lobe.
 Natica canrena or allied forms are widespread in the Caribbean region in formations of Miocene and Pliocene


age. N. precanrena F. Hodson (Hodson, Hodson, and Harris, 1927, p. 68, pl. 36, figs. 2, 6, 9), a small Venezuelan early Miocene species (height 6.8 millimeters), has a high spire, small initial whorl, and closely spaced axial grooves. It has, however, a higher spire and a wider umbilicus than small specimens of N. stenopa.
 Occurrence: Lower, middle, and upper parts of Gatun formation (middle and late Miocene). Lower' part, localities 136, 137, 137a, 138, 138a. Middle part, eastern area, localities 146, 147b, 147g, 147h (incomplete, identification doubtful), 151, 155, 155c, 157; western area, localities 161, 161a, 161c, 161d, 170, 170a. Upper part, eastern area, localities 175, 176a, 177b, 177c; western area, localities 183, 185.
 Genus Stigmaulax Mdrch
M6rch, Catalogus conchyliorium Comes de Yoldi, pt. 1, p.
 133, 1852.
Type (logotype, Harris, Catalogue of Tertiary Mollusca in the
 British Museum; pt. 1, Australasian, p. 262, 1897): Natica
 sulcata Born (Nerita sulcata Born), Recent, West Indies.
 Stigmaflax, like Naticarius, lives in American tropical and subtropical waters on both sides of Central America. It is found in the late Tertiary of the same region, the earliest species being of early Miocene age.
 Stigmaulax guppiana (Toula)
 Plate 20, figures 11-16
Natica guppiana Toula, K. k. Geol. Reichsanstalt Jahrb., Band
 58, p. 696, pl. 25, fig. 6, 1909 (Miocene, Canal Zone). Hodson, Hodson, and Harris, Bull. Am. Paleontology, v. 13, no. 49,
 p. 67, pl. 36, figs. 1, 4, 1927 (Miocene, Venezuela).
Nlatica guppyana Toula, Engerrand and Urbina, Soc. Geol.
 Mexicana Bol., v. 6, p. 130, pl. 60, figs .53, 54, 55 (reproduction of Toula's illustration), 1910 (Miocene, Mexico). Brown and Pilsbry, Acad. Nat. Sci. Phila. Proc., v. 63, p. 360, 1911 (Miocene, Canal Zone). Olsson, Bull. Am. Paleontology, v. 9, no. 39, p. 156, pl. 13, figs. 13-15, 1922 (Miocene, Panamd, Costa Rica). Anderson, California Acad. Sci. Proc., 4th ser., v. 18, no. 4, p. 123, 1929 (Miocene, Colombia). Tucker and Wilson, Bull. Am. Paleontology, v. 18, no. 65, p. 13, pl. 2, figs. 3, 4, 1932 (Miocene, Florida). Mansfield, Florida Dept.
 Conservation, Geol. Bull. 12, p. 10, 13 (lists), 1935 (Miocene,
 Florida).
Natica (Stigmaulax) sulcata guppiana Toula, Rutsch, Schweizer.
 Palacont. Gessel. Abh., Band 54, no. 3, p. 51, pl. 1, fig. 15 (type),
 1934 (Miocene, Canal Zone).
Natica (Naticarius) guppyana Toula, Oinomikado, Geol. Soc.
 Japan Jour., v. 46, p. 621, pl. 29, fig. 18, 1939 (Miocene,
 Colombia).
Natica (Stigmnaulax) guppiana Toula, Gardiner, U. S. Geol. Survey Prof. Paper 142, p. 546, pl. 59, fig. 9 (reproduction of Toula's illustration), 1947 (Miocene, Florida). Natica (Stigmaulax) guppiana toulana Gardner, idem, p. 547, pl. 59, figs. 7, 8, 1947 (Miocene, Florida). Natica (Stigmaulax) guppyana Toula, Marks, Bull. Am. Paleontology, v. 33, no. 139, p. 98, 1951 (Miocene, Ecuador). Operculum (sp.?), Toula, K. k. Geol. Reichsanstalt Jahrb., Band 61, P. 511, p1. 31. fCo. 26. 1911 (Miocene. Canal Zone).


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