166 CHITON. 



Girdle (pi. 32, figs. 53) covered with solid, convex, subcarinated 

 imbricating scales. Length 68, breadth 50 mill. 



Guaymas, West Mexico, to Panama and West Columbia. 



Chiton stokesii BROD., P. Z. S., 1832, p. 25. SOWB., Conch. 

 Illustr., f. 24. REEVE, Conch. Icon., t. 1, f. 4. MORCH, Mai. Bl. 

 vii, p. 176. Chiton patulus SOWB., Charlesworth's Mag. Nat. Hist. 

 1840, p. 291 ; Conch. Illustr., f. 134. REEVE, Conch. Icon., f. 30. 

 C. interruptus CPU., MS. 



The sculpture of the lateral areas is peculiar, being something like 

 the meshes of a stretched net, but the cords or riblets are irregularly 

 granulose. In uniting the C. patulus of Sowb. to stokesii, I quite 

 agree with Carpenter, who writes as follows: The form patulus is 

 typically " engine-turned " on the terminal valves, with strong rugae 

 on the sides, and larger scales on the girdle. A young specimen 

 sent by Mr. Cuming has only 18 slits in the tail plate. The typical 

 stokesii has the terminal rugse radiating, and sometimes a row of 

 color dots at the sutures. The bulk of the Panama and San Juan 

 specimens (of which I have examined many hundreds) are so 

 variously intermediate between the two forms that I find it impos- 

 sible to separate them even as varieties. The scales are extremely 

 deciduous, and specimens in good condition are not often found. 

 It was often the custom of Mr. Cuming to select extreme forms for 

 his cabinet; and these being described and figured as the normal 

 types of species are very apt to mislead students who work by single 

 specimens. 



C. VIRGULATUS Sowerby. PL 32, figs. 54, 55, 56. 



Shell oblong, parallel-sided, rather elevated, the dorsal ridge car- 

 inated, side-slopes straight. Lateral areas and end valves olive- 

 brown, or like the central areas which are green, longitudinally 

 clouded with blackish ; girdle firm and valid, transversely or longitu- 

 dinally banded. 



The lateral areas are raised and sculptured with numerous (8-10) 

 radiating riblets, which have a tendency to split or branch. Central 

 areas sculptured with longitudinal riblets which at the sides diverge 

 a little and are nearly as coarse as those of the lateral areas, but 

 become finer and parallel to the ridge toward the middle. End 

 valves having close radiating riblets; apex of tail valve anterior. 



Inside dark blue-green; sutural-plates high, blue-green. Sinus 

 deep angular and toothed. Anterior valve having 21-22, central 



