102 ISCHNOCHITON. 



Chiton textilis var. Sows., Conch. Illustr. f. 61, according to 

 Reeve. Chiton reticulatus Rv., Conch. Icon. pi. 15, fig. 83 (1847). 

 Ischnochiton reticulatus CPU., MS. 



Reeve states that this is the textilis of Sowerby but not of Gray, 

 and he is probably right, although his own identification of textilis 

 Gray is erroneous. Carpenter gives these notes upon Reeve's type 

 specimen : One specimen, which is over-colored and over-drawn in 

 Reeve's illustration. It looks to me like a fine textilis, as Sowerby 

 seems to have taken that species, but I have no textilis by me for 

 comparison. It is very light brown, with little black irregular dots 

 which appear to be adventitious. Girdle typically Ischrioid, with 

 moderate-sized striated imbricating scales. Fine radiating ribs on 

 the lateral areas, very numerous on the terminal valves ; honey- 

 combed in the middle ; jugum very much rounded. Anterior valve 

 with 14, central valve 1, posterior valve 12 slits; teeth sharp; sinus 

 very broad and flat, not toothed. Length 30}, breadth 16 mill. 



Compare textilis Gray, from which this differs in coloration and 

 apparently in sculpture. 



3. Group of I. rissoi. 



Small species having longitudinal riblets upon the central areas, 

 and continuing backward over the lateral areas. These are closely 

 allied to the group of /. striolutii*. 



Distribution : Mediterranean, African and West Indian. 



I. RISSOI Payraudeau. PL 20, figs. 1-7. 



Shell oblong, elevated, the back regularly arched or subcarinated, 

 side slopes convex. Surface longitudinally lirate on the intermedi- 

 ate, concentrically on the end valves. Color pale brown-olive, the 

 lateral areas and end valves more or less maculated with snow-white 

 and brown. 



The lateral areas are moderately raised and sculptured with 

 coarse, flat, uneven-edged longitudinal riblets, which are separated 

 by narrow punctate intervals and are frequently irregular ; under 

 a higher power of the microscope the surface appears to be min- 

 utely punctate, the dots whitish. The central areas have close, fine 

 riblets in the same direction, somewhat finer on the dorsal ridge, 

 and giving way to a minute pu notation in the region of the beak of 



