GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


sculpture suggest T. plebeia Say, of the Miocene of Maryland. T. plebeia has similar early sculpture, but its growth-line sinus is narrower and deeper, and its growth-line angle is narrower.
 T. matarucana occurs in the Gatun formation. It is locally abundant in the lower part of the formation and rare in the middle part.
 Occurrence: Lower and middle parts of Gatun formation (middle Miocene). Lower part, localities 135 (identification doubtful), 136, 136a, 137, 137a, 138a. Middle part, eastern area, locality 144a (identification doubtful); western area, locality 161c. Uramaco (middle Miocene) and La Vela (late Miocene) formations, Falc6n, Venezuela.
 Subgenus?
 Turritella gatunensis gatunensis Conrad
 Plate 23, figures 4, 5, 9, 14
 Turritella gatunensis Conrad, Pacific R. R. Expl., v. 6, Geol.
 Rept., p. 72, pl. 5, fig. 20, 1857 (Miocene, Gatun, Panamd).
 (Reprinted, U. S. Geol. Survey Prof. Paper 59, p. 178, 1909.) Dall, Wagner Free Inst. Sci. Trans., v. 3, pt. 2, p. 310 (part, not pl. 17, fig. 10=T. atacta Dall), 1892 (Miocene, Gatun, Panamd). Brown and Pilsbry, Acad. Nat. Sri. Phila. Proc., v. 63, p. 358, pl. 27, figs. 4, 5. 9, 1911 (Miocene, Canal Zone).
 Olsson, Bull. Am. Paleontology, v. 9, no. 39, p. 148, pl. 14, figs. 12, 13, 1922 (Miocene, northwestern Panamd, Costa Rica). Anderson, Calif. Acad. Sci. Proc., 4th ser., v. 18, no. 4, p. 120, 1929 (Miocene, Colombia). Li, Geol. Soc.
 China Bull., v. 9, p. 267, pl. 6, fig. 49, 1930 (Miocene, Panamd Bay; Miocene, Gatun, fide Pilsbry, Acad. Nat. Sci. Phila.
 Proc., v. 83, p. 432, 1931). Marks, Bull. Am. Paleontology,
 v. 33, no. 139, p. 100, 1951 (Miocene, Ecuador).
Turritella cf. T. gatunensis Conrad, Weisbord, Bull. Am. Paleontolegy, v. 14, no. 54, p. 33, pl. 9, fig. 7, 1929 (Miocene, Colomhis).
Turritella gaeunensis lavelana Hodson, idem, v. 11, no. 45, p. 23,
 pl. 18, fig. 6, pl. 19, fig. 7, 1926 (Miocene, Venezuela).
Turritella conradi Toula, K. k. Geol. Reichsanstalt Jahrb.,
 Band 58, p. 694, pl. 25, fig. 4, 1909 (Miocene, Canal Zone). Not Turritella gatunensis Conrad, Gabb, Acad. Nat. Sci. Phila. Jour., 2d ser., v. 8, p. 342, pl. 44, figs. 10, 10a, 1881 (Oligocene(?), Costa Rica;= T. tristis Brown and Piisbry). Joukowsky, Soc. Phys. Histoire Nat. Geneva M6m., t. 35, p. 163 (list), pl. 6, figs. 26, 27, 1906 (Oligocene, Panamd;= T. meroensis Olsson). Maury, Bull. Am. Paleontology, v. 10, no. 42, p. 229, pl. 42, fig. 12, 1925 (Miocene, Trinidad;= T. caronensis Mansfield, described as a subspecies of T. gatunensis). Mansfield, Washington Acad. Sci. Jour., v. 28, p. 102, figs. 1-3, 6, 1938 (Oligocene, Florida).
 Moderately large, slender. Posterior part of whorls constricted, anterior part concave between primary spirals. Sculpture consisting of a primary spiral near, but generally behind, middle of whorl, a second primary at anterior third to fourth, and numerous minor spirals. Microscopic spirals generally visible on late whorls. A minor spiral lying behind, and close to, middle primary is almost, or quite, as strong as primaries on some specimens. On a few specimens a minor spiral in front


of anterior primary or between primaries is accentuated. Primaries decreasing in strength on last whorl or two of some specimens. As they decrease, anterior part of whorl becomes more inflated. Spirals slightly undulated by axial waves on a few specimens. Protoconch cylindrical, of two inflated whorls. Early sculptured whorls attenuated. A very strong middle spiral, forming a strong median carina, a very weak spiral adjoining anterior suture, and a very weak spiral half-way between them appear on first sculptured whorl. The strong middle spiral is the middle primary of later whorls. The weak spiral adjoining the anterior suture gradually enlarges and becomes the anterior primary. Other weak spirals appear on third or fourth sculptured whorl. Base sculptured with numerous low minor spirals. Growth-line sinus wide and shallow, the apex between primaries; growth-line angle wide. Interior of late whorls smooth or bearing narrow spiral ridges of varying strength.
 Height (almost complete) 58.5 mm, diameter 15 mm (largest figured specimen).
 Type: Lost.
 Type locality: Gatun, Canal Zone.
 Turritella gatunensis, like T. altilira, was based on. fossils collected by Newberry at Gatun. The type of T. gatunensis is lost. As Conrad's illustration is even cruder than his representation of T. altilira, the identification rests primarily on the brief and unsatisfactory description. The collection that furnished a topotype of T. altilira (locality 150a) includes the traditional T. gatunensis, but the preservation is not good enough for designation of a neotype. The specimens shown on plate 23, figures 4, 9, collected at the Gatun Locks site, 250 meters west of Gatun, are considered representative of the typical form.
 The typical form of T. gatunensis probably is represented in the calcareous sandstone member of the Caimito formation in Madden basin. It is locally abundant in the lower part of the Gatun formation, widespread and locally abundant in the middle part, rare in the upper part in the eastern area, and probably occurs in the Toro limestone member of the Chagres sandstone.
 Intermediate whorls are characterized by the two primary spirals and the concave space between them. Early sculptured whorls are attenuated and are very strongly carinate at the middle of the whorl. Late whorls, however, are variable in sculpture and whorl profile. Nevertheless the basic pattern of a middle and anterior primary is more or less discernible. This basic pattern, the constriction of the posterior part of whorls, and the growth line are the most reliable features for identification of late whorls. Most of the shells from the lower part of the Gatun formation are


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