18 H. Doc. 129. 



1 



cles, and flattened at the summit. Spire conical ; penultimate whorl 

 with one series of tubercles. 



Locality. Tulare Valley. (Found with Meretrix Tularana, Con., 

 pi. ii, fig. 22 and 32a. Both specimens are clay casts, hut very 

 perfect. W. P. 5.) 



III. TERTIARY SHELLS OF THE ISTHMUS OF DARIEN. 



MIOCENE : 



Mr. Blake has 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. 



GRATELUP1A? Desmoulins. 



48. G. ? MACTIIOPSIS, Con., pi. , fig. 54. Triangular, inequila- 

 teral; dorsal margins equally oblique, straight; basal margin rounded 

 anteriorly, slightly curved, posteriorly, posterior extremity truncated, 

 direct, considerably above the line of the base. 



Locality. Isthmus of Darien. 



MERETRIX. 



49. M. DABIENA, Con., pi. , fig. 55. Obtusely and obliquely sub- 

 ovate; ventricose; inequilateral; anterior extremity angulated and 

 situated much nearer the beak than the base; anterior dorsal line 

 straight and oblique ; beak not prominent ; basal and posterior mar- 

 gins profoundly rounded. 



Locality. Occurs with the preceding. 



TELLIIVA, Lin. 



50. T. DARIENA, Con., pi. , fig. 53. Subtriangular, compressed; 

 anterior hinge-margin rectilinear, very oblique, extremity truncated, 

 direct; posterior extremity regularly rounded ; base moderately curved. 



Locality. Occurs with the preceding. 



IV. 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 con- 

 tains many of these casts, but the descriptions are principally based 

 upon the drawings made at the locality by Mr. Blake. 



NATICA. 



51. N. OCOYANA, Con., pi. vi, fig. 57. Spire conical, volutions three 

 or four, rounded on the sides, depressed above ; body whorl very wide, 

 depressed. 



Locality. Ocoya creek. W. P. Blake. 



52. N. GENICULATA, Con., pi. vi, fig. 6*7. Globose, volutions angu- 

 lated above : spire short, conical ; body whorl contracted near the 

 summit. 



Locality. Ocoya creek. W. P. Slake. 



