OF CONCHOLOGY. 143 



amined a very large series, extending from Sitka to Monterey. 

 In such cases the only satisfactory way of determining specific 

 differences is to compare normal undistorted specimens of the 

 same age. 



E. saxicola is characterized by a straw yellow or dark brown, 

 thick, strong epidermis, which always breaks the thin shell in 

 drying. This epidermis is marked by a peculiar smoothness of 

 its exterior, though puckered up, wrinkled and folded to a great 

 extent. The pinched up wrinkles are characteristic. It is dis- 

 tantly radiately striate, especially toward the posterior end. 

 These striae are more properly raised folds. The substance of 

 the shell has a characteristic porcellanous texture and appear- 

 ance, but slightly nacreous, usually livid, though rarely white, 

 but never brilliantly pearly. In normal specimens the shell is 

 more or less truncate at each end, especially the anterior end, 

 which is further marked by two more or less evident ridges, ex- 

 tending from the beaks. It always has a large ventral gape. 



E. Scammoni can then be readily distinguished by its nacre, 

 its characteristic epidermis, which does not contract and break 

 the shell, and which is striated in a totally different way from 

 that of saxicola. It has not the ridges or ventral gape alluded 

 to. My specimens agree exactly with each other, in all respects, 

 and are not distorted in the least. 



Entodesma diaphana, Cpr. 



Some shells in the Smithsonian collection, thus marked, ap- 

 pear to be worn specimens of what I called (in MSS.) Ento- 

 desma spongiaphila, in 1866. Mine were from Monterey. The 

 others are from San Diego and Cape St. Lucas. Dr. 

 Carpenter's type was from Mazatlan. He also unites 

 with it Lyonsia i?iflata, Conr., a species from Guayaquil, of 

 which the type has not been examined by either Dr. Carpenter 

 or myself. Conrad's figure represents a very different looking 

 shell. L. califomiea, Conrad, probably includes bracteata, Grid., 

 and nitida, Gould. I should be inclined to include Conrad's 

 iniiata with it also, from the figure, if such a course were admis- 

 sible. Conrad, in his catalogues, has it in both Lyonsia and 

 Entodesma, with the same references. 



If E. diaphana, Cpr., be the same as my MSS. species, it is 

 undoubtedly perfectly distinct from the others. The practice 

 of combining species, autoptically unknown to the combiner, is 

 most pernicious, and produces far more confusion than the de- 

 scription of mere varieties as specifically distinct, though the 

 latter is objectionable enough. 



