CHITON. 167 



valves 1 or 2, posterior valve 19-20 wide spongy slits; teeth wide, 

 blunt, pectinated ; eaves short, narrow, spongy. 



Girdle compactly covered with solid, shining convex scales (pi. 

 32, fig. 56.) 



Magdalena Bay, L. California] Gulf of California. 



Chiton virgulatus SOWB. in Charles worth's Mag. Nat. Hist. 1840, 

 p. 291 ; Conch. Illustr., f. 132. REEVE, Conch. Icon., t. 21, f. 140. 



This species is allied to 0. stokesii, but differs in being narrower, 

 more elevated, differently colored, in having the riblets finer, more 

 numerous and less anastomosing, in the color of the interior and in 

 the number of slits, which is much greater in the end valves of this 

 species than in those of C. stokesii, and in some of the intermediate 

 valves there are two slits in one or both sides. The entire surface, 

 as usual in this genus, is microscopically granulated. The girdle- 

 scales are finer and smoother than in C. stokesii, and the sutural- 

 plates are different in form. 



A square mm. of the girdle is shown by the dotted line in fig. 56. 



It has been reported from Australia, but erroneously. Many spec- 

 imens are before me from the localities given above. 



The remarkable feature of this species is that it forms a perfect 

 transition between the restricted genus Chiton and the section 

 Radsia. Some specimens have two slits in one end of one valve 

 only ; others have two slits in the majority of the valves ; and 

 scarcely two are alike in the arrangement of 1- and 2-slit insertion- 

 plates. I have examined the interior in about a dozen individuals 

 and have always found at least one insertion-plate Radsioid, but 

 probably a larger series would reveal specimens with the normal 

 plates of Chiton s. s. 



C. GRANOSUS Frembly. PI. 30, figs. 27, 28. 



Shell oval-oblong, moderately elevated, scarcely carinated, the 

 side-slopes somewhat convex. Slack, having a white stripe on each 

 side of the central line, clouded with whitish between the stripes. 



Lateral areas bearing three or four rows of bead-like pustules, on a 

 smooth ground ; central areas having a narrow smooth dorsal band, 

 the MtV/e* (pleura) covered with close, fine longitudinal riblets, which 

 are more or less crenulated by the growth-lines. End valves hav- 

 ing rounded pustules in radiating rows or irregularly scattered ; 

 umbo of tail valve near the front margin. 



