CALLISTOCHITON. 265 



very closely and finely latticed across. Anterior valve having seven 

 very strong ribs, each divided by a shallow median groove. Poste- 

 rior valve elevated, having the mucro directly over the posterior edge, 

 lie hinder area not higher than the area in front of it; posterior 

 slope vertical, convex, sculptured with five very strong, deeply 

 separated ribs, which are granose above, and subdivide into several 

 riblets each toward the lower margin. 



Interior bluish-white ; sutural-plates slightly connected across the 

 rounded sinus. Anterior valve having 9, central valves 1, poste- 

 rior valve 13-20 slits ; teeth short, rather sharp and smooth, hardly 

 projecting below the eaves, thickened along the slits outside; eaves 

 broad, solid. 



Girdle narrow, thin, covered with excessively minute, closely 

 imbricating, striated scales. 



Length 22, breadth 9 mill. 



Monterey, California. 



Callistochiton fimbriatus CPR., MSS. 1875. Not Callochiton fim- 

 briatus Cpr. in COOPER, Geographical Catalogue of the Mollusca 

 found west of the Rocky Mountains, between Latitudes 33 and 49 

 North (Geol. Surv. of Cal.), p. 23, 1867 (no description),^ Callisto- 

 chiton pulchellus, Cpr. MSS. 1875. 



? Chiton ( Callochiton) fimbriatus Cpr., ORCUTT, Proc. U. S. Nat. 

 Mus. 1885, p. 544 (1885), no description. Not Chiton fimbriatus 

 SOWB. 



This species is readily separated from the next by the smaller 

 number of ribs on the head and tail valves, the less distinctly bicos- 

 tate lateral areas, and the far less elevated tail valve, which has, 

 besides, a posterior terminal mucro. 



The specimens before me were collected by Henry Hernphill at 

 Monterey. A species under this name has been reported from San 

 Diego and from Catalina Island, but the identity of the specimens 

 with the present species is open to doubt, although its occurrence in 

 those places is not improbable. 



The name of this species is involved in some obscurity, owing to 

 the fact that no diagnosis or description whatever has heretofore been 

 published, although the name fimbriatus has appeared in several 

 lists. This much however is certain : that the original fimbriatus 

 Cpr. of Cooper's Catalogue, the unique type of which is said to be in 

 the Smithsonian Institution collection, is not the fimbriatus of Car- 

 penter's later MSS. (Vide Carpenter's MSS. vol. I, p. 135) ; and we 



