27 



disposed asperities on the surface of a rasp, and entirely unlike 

 any markings seen on the living species. 



108 — Is referred by 'Mr. Carpenter to Janira (= typical Pectm, Muller), 

 and is one of the forms upon which Mr. Conrad proposed to 

 establish a new genus Lyropecten. It differs from the typical 

 Janiras, in .having both valves distinctly and very nearly 

 equally convex, and the hinge provided with three strong di- 

 verging teeth on each side of the cartilage pit, but feebly 

 represented by the slende» ridges in the hinge of Janira. 



Ill =H'ucula impressa, Conkad, U. S. Expl. Expd. X, 722. 



llS^Leda 'Willamettensis, Shdmard, Trans. St. Louis Acad. Sci. I. 



liy^Nucula peuita, Conkad, Am. Jour. Sci. V, (2), 433, Fig. 9. 



119 = Leda Oregona, Suumakd, Trans. St. Louis Acad. I. 



127 = Nucula divaricata, Coxrad, Am. Jour. Sci. V, (2) 1848, 432: 



(not iV. divaricata, Hunds, 1844). The name of this species should have 

 been Nucula {Acila) Conradi, iu the list, since it belongs to 

 H. and A. Adams' group Ac'da. 



Since the foregoing list was partly stereotyped, I see Mr. 

 Carpenter refers this species to the recent Nucula castrensis, of 

 Hinds, 1844. I have no specimens of the recent shell at hand 

 for comparison, and have seen only imperfect examples of the 

 fossil species. On comparing the latter and Mr. Conrad's 

 figures in the Journal of Science, and the Report of the U. S. 

 Exploring Expedition, with Dr. Hind's figure of N. castrensis, 

 I find that the fossil shell, in addition to being much larger, 

 with more prominent beaks, differs in having the imaginary 

 line from which the surface striae divaricate, extending directly 

 from the beaks to the posterior basal magin ; while in the figure 

 of N. castrensis, it is represented as curving down so as to in- 

 tersect the base near the middle. Again, the divaricating 

 markings are proportionally larger, and less numerous on the 

 figure of iV. castrensis, while On the posterior dorsal region 

 they are drawn as if extending back nearly parallel to the 

 dorsal margin, instead of curving gracefully upwards so as to 

 intersect the cardinal border, as in the fossil shell. I am aware 

 these differences may be due to errors in Dr. Hind's figure, but 

 when we bear in mind that the fossil shell is also so nearly 

 like another found associated with Baculites, Ammonites, and 

 other cretaceous types in California, that even Mr. Conrad, on 

 comparing specimens, pronounced them identical, we may be 

 also excused for hesitating to admit the identity of the Miocene 

 and recent forms, until verified by the comparison of good 

 examples of each, showing all the internal and external cha- 

 racters. 



i40 = Pectenculus nitens, Coxkad, U. S. Expl. Exp. X, 726, 18, 9, a, b. 

 In Mr. Carpenter's first Report to the British Assoication on 



