26 



cimens, however, from Astoria, I find that they show, under 

 the microscope, no traces of the punctate structure character- 

 izing the Terebraiulidip, although they exhibit, by transmitted 

 light, very distinctly the usual fibrous texture. From this I 

 infer that the species can neither be a Terebratula, nor a 

 Waldkfimia, but belongs to the genus Rhynchonella. None 

 of tlie specimens are in a condition to show the nature of the 

 foramen, nor any of the internal characters of the shell ; but 

 from all that can be determined, I am inclined to think it related 

 to the recent R. psittacea, though it seems to be more finely 

 striated, and has apparently a less prominent beak. 



53 — Since the foregoing list of Miocene shells was partly stereotyped, Mr. 

 Conrad informs me that he now thinks his Ostrea Hermanni 

 probably a cretaceous species. 



65 — Mr. Carpenter refers this species with doubt, in his British Asso- 

 ciation Report, to the recent P/acunomin inacroschisma, Des- 

 hayes. The type specimen, however, is too imperfect to be 

 satisfactorily compared with anything. 



70 — Referred with doubt by Mr. Carpenter to the recent H. gigantem Gfray. 

 On comparison, I am inclined to think they may be identical, 

 but the specimens of the fossil are by no means sufficient to 

 decide sxich a question, particularly in a genus like this. 



77^ Janira afEnis, Tcomey and Holmes, Plioc. Foss. S. Car. 26, 8, 56. 

 I do not adopt the name Jditirn, because it was founded upon 

 the typical forms of the older genus Pecten, Muller. 



79 — This and most of the following species here retained under the name 

 Pecten are distinct from that genus, as properly restricted by 

 Lamarck, to such forms as P. Jacobius, and P. maxhnus, though 

 it is not considered desirable to attempt to distribute them into 

 proper groups with the material at hand. 



84 = Janira bella, Co.vkad, Pac-ifi^ R. R. Rept. VI, 71, III, 16. 



95 — This should probably have been printed Amussium propatulum in 

 the list ; it difl"ers, however, from the typical species of that 

 genus in the possession of large external radiating costae, and 

 a distinct byssal sinus. 



I observe Mr. Carpenter suggests that if not identical with 

 the recent Amussium caurinum, Gould, this shell is most closely 

 related. It is undoubtedly related to that species, as many of 

 our Miocene shells are to their living representatives ; but on 

 comparison, I find that they may be readily distinguished. 

 In the first place the A. cmtrinum has from 20 to 22 costse to 

 each valve ; while the fossil species has uniformly only about 

 16, which are also wider in proportion to the depressions 

 between. Again, when the surface of the fossil shell is well 

 preserved it shows, under a magnifier, a very peculiar and 

 beautiful style of sculpture resembling somewhat the regularly 



