Family CREPIDULIDAE
 Genus Crepidula Lamarck
 Lamarck, Soc. Hist. Nat. Paris Mem., p. 78, 1799. Type (monotype): Patella fornicata Linn6, Recent, eastern United States.
 Molds from the Culebra formation are identified as Crepidula sp.

 Crepidula of. C. maculosa Conrad Plate 19, figures 4, 5
 Crepidula galunensis Toula, K. k. Geol. Reichsanstalt Jahrb.,
 Band 61, p. 498, pl. 31, figs. 12a, b, 1911 (Miocene, Canal
 Zone).
 Of medium size, moderately narrow, moderately vaulted. Protoconch of small specimens consisting of about 1)% whorls of neritoid outline. Deck of small specimens moderately deep seated, bearing a wide shallow median indentation.
 Length 28.5 mm, width 17.5 mm, approximate height 10.5 mm (figured specimen).
 A species of Crepidula from the Gatun formation is comparable to the Recent C. maculosa, to which attention has recently been called (Stingley, 1952). As pointed out by Stingley, C. maculosa has a pedal muscle scar adjoining the adapical insertion of the deck and the edge of the deck has a very slight median indentation, whereas the better known and more northern C. fornicaoa (with which C. maculosa has been confused) lacks the muscle scar and has a pronounced median indentation.
 The only fairly large shell from Gatun (pl. 19, figs. 4, 5) is attached to a crab carapace and the interior is inaccessible. Owing presumably to inequalities on the carapace, this shell has two faint depressions and correspondingly modified growth lines. The other shells (all of which are small, ranging in length from 1.5 to 12 millimeters) evidently represent the same species as the fairly large specimen. Two that are moderately small show the muscle scar of C. maculosa.
 According to Toula's description and illustration, C. gatunensis was based on a small shell (length 2.8 millimeters) like those in the collections at hand. That name is available, should the name C. maculosa be found to be inappropriate for the fossils.
 Though C. fornicata is recorded from the Miocene of Trinidad (Maury, 1925, p. 244), it is unlikely that that species lived in the Caribbean Sea at any time.
 Occurrence: Lower, middle, and upper parts of Gatun formation (middle Miocene). Lower part, localities 137, 138. Middle part, eastern area, localities 147b, 155c, 157. Upper part, eastern area, locality 178.


79


 Crepidula plan Say
 Plate 19, figures 1-3
 Crepidula plana Say, Acad. Nat. Sci. Phila. Jour., 1st ser. v. 2
 p. 226, 1822 (Recent, Maryland to Florida). Dall, Wagner Free Inst. Sci. Trans., v. 3, pt. 2, p. 318, 1892 (Miocene to Recent, eastern United States). Brown and Pilsbry, Acad.
 Nat. Sci. Phila. Proc., v. 63, p. 360, 1911 (Miocene, Canal Zone). Brown and Pilsbry, idem, v. 65, p. 495, 1913 (Pleistocene, Canal Zone). Pilsbry, idems, v. 73, p. 385, 1922 (Miocene, Dominican Republic). Olsson, Bull. Am. Paleontology, v. 9, no. 39, p. 159, 1922 (Miocene, northwestern Panamd). Gardner, U. S. Geol. Survey Prof. Paper 142, p. 0565, 1947 (Miocene, Florida); see this publication for other
 citeios.
 Crypta fornicala (Linn), Gabb, An. Philos. So. Trans., v. 15,
 p. 242, 1873 (_Miocene, Dominican Republic).
 Of medium size, narrow, compressed, flat or concave. Protoconeh of immature shells consisting of 1% to 1Y2 rapidly enlarging whorls of neritoid outline, destroyed at later stage by encroachment of aperture. Deck bearing a moderately deep narrow abapical marginal indentation and a moderately deep very wide median indentation.
 Length 15 mm, width 10.5 mm, height 2 mm (larger figured specimen).
 Slipper limpets recovered from the apertures of Gatun coiled gastropods agree closely with the Recent Crepidula plana. All the fossils were found in the lower part of the formation. C. plan is already recorded from the Gatun formation of the Canal Zone and from late Miocene strata in northwestern Panama'.
 A species of Crepidula that has a similar outline and similar deck characters is living in the eastern Pacific Panamic region. It presumably is C. nivea C. B. Adams, but is generally known as C. numsaria Gould. The few specimens of this species from Panamd in the collection of the U. S. National Museum have slightly deeper deck indentations than C. plan.
 Occurrence: Lower part of Gatun formation (middle Miocene), localities 137a, 138, 138a. Middle part of Gatun formation (middle Miocene), eastern area (Brown and Pilsbry). Late Miocene, Water Cay, Panama. Miocene, Dominican Republic. Early to late Miocene, Maryland to Florida. Pliocene, North Carolina to Florida. Pleistocene, Massachusetts to Florida, Canal Zone. Recent, Prince Edward Island, Canada, to Texas and the West Indies.
 Family Calyptraeidae
 The genus Cheilea is not represented in the collections at hand. Cheilce princetonia Browli and Pilsbry (1911, p. 360, fig. 2), based on an internal and external mold from the Gatun formation, may be conspecific with the Cheilea from the Bowden formation of Jamaica


GASTROPODS: TROCHIDAE TO TURRITELLIDAE