MUSEUM OF COMPARATIVE ZOOLOGY. 165 



irregular in shape. A few lines may also be dropped, perhaps some added, or the 

 entire surface may be modified in obedience to the laws of the mechanical skill 

 possessed by the individual, and the affinity of matter secreted by the animal, for 

 the purpose of constructing the shell. An examination of a large number of 

 Selenites concarus, and of our West Coast forms, convinces one that the entire group 

 of American Selenites is the offspring of a single common type. 



The above is Mr. Hemphill's description, from " The Nautilus," Vol. IV. 

 p. 42, 1890. 



Selenites Duranti, var. Catalinensis, Hemphill. 



Plate II. Fig. 3. 

 I figure an authentic specimen. See Third Suppl., p. 221. 



Selenites Vancouverensis, var. transfuga, Hemphill. 



Shell very much depressed, planulate, broadly umbilicated, of a dirty white 

 color; whorls 3^ or 4, flattened above, more rounded beneath, with regular strong 

 rib-like striae ; suture well impressed, becoming deeper and channel-like as it ap- 

 proaches the aperture; aperture hardly oblique, slightly flattened above, with a 

 tendency to a corresponding depression below ; lip simple, roundly thickened inter- 

 nally, its terminations approaching, forming in some specimens a short columellar 

 lip, joined by a heavy raised callus in very adult specimens. Height -^ inch, 

 greatest diameter ^, lesser ^ inch. 



San Diego, California, to Todos Santos Bay, Lower California. 



This is the small flat shell that has been distributed as a variety of sportella, and 

 also as a variety of Voyanus. I find, however, on comparing it with the typical 

 Voyanus collected by me last fall, that it is quite a different shell. The ribs are 

 closer and finer than either sportellus or Voyanus, the umbilicus is much larger, 

 and it is a very much more depressed shell. I consider it, however, a deserter from 

 the Northern forms, and name it accordingly. It is a much larger and a more 

 globose form than simplilabris of Ansey. 



The above is Mr. Hemphill's description. 



Selenites Vancouverensis, Lea. 



The only diflerences that I can detect between this shell and Selenites concava, 

 Say, are these. The umbilicus in the California shells is a little more contracted, the 

 color is a shade darker, the striae are a little closer, stronger, and more regular, and 

 the body whorl is a little more flattened at the aperture. Height § inch, breadth 

 ^ inch. 



Sonoma Co. to Santa Cruz Co., California. 



The above is IVIr. Hemphill's description of what he calls S. concavus, var. 

 occidentalis. 



