328 
APPENDIX. 
III. TERTIARY SHELLS OF THE ISTHMUS OF DARIEN. 
MIOCENE? 
Mr. Blake lias forwarded me casts of three bivalves. They are forms which are new to me, 
and probably Miocene species. The Gratelupia , except in being truncated posteriorly, much 
resembles G. Hydeana, Conrad, an Eocene fossil. 
GRATELUPIA? Desmoulins. 
49. g. ? mactropsis, Con , PL YI. fig. 54.—Triangular, inequilateral; dorsal margins equally 
oblique, straight; basal margin rounded anteriorly, lightly curved, posteriorly, posterior ex¬ 
tremity truncated, direct, considerably above the line of the base. 
Locality. —Isthmus of Darien. 
MERETRIX. 
50. m. dariena, Con., PL YI, fig. 55.—Obtusely and obliquely subovate; ventricose; inequi¬ 
lateral ; anterior extremity angulated, and situated much nearer the beak than the base ; ante¬ 
rior dorsal line straight and oblique; beak not prominent; basal and posterior margins pro¬ 
foundly rounded. 
Locality. —Occurs with the preceding. 
TELLINA, Lin. 
51. T. dariena, Con., PI. VI, fig. 53.—Subtriangular, compressed; anterior binge-margin 
rectilinear, very oblique, extremity truncated, direct; posterior extremity regularly rounded ; 
base moderately curved. 
Locality. —Occurs with the preceding. 
IY. MIOCENE FOSSILS FROM OCOYA CREEK. 
The following are descriptions of some of the fossils from Ocoya creek, (Pose creek,) which 
occur only as casts. The collection contains many of these casts, but the descriptions are prin¬ 
cipally based upon the drawings made at the locality by Mr. Blake. 
NATICA. 
52. n. ocoyana, Con., PI. VII, fig. 57 and 57 a. —Spire conical, volutions three or four, 
rounded on the sides, depressed above ; body whorl very wide, depressed. 
Locality .—Ocoya creek. 
52. n. geniculata, Con.. PI. VII, fig. 67.—Globose, volutions angulated above ; spire short, 
conical; body whorl contracted near the summit. 
Locality. —Ocoya creek. 
Resembles N. alveata, Con., of the California Eocene. 
BULLA. 
54. b. jugularis, Conrad, PI. VII, fig. 62, 62a, 62 b. —Oblong elongated, much contracted 
toward the apex ; acutely rounded at the base. 
Locality. —Ocoya creek. 
PLEUROTOMA 
55. p. transmontana, Conrad, PL VI, fig. 69.—Fusiform, with rugose revolving lines and 
