ISCHNOCHITON. 113 



The outside of this shell so much resembles the young of Chiton 

 stokesii that specimens may have been distributed under that name. 

 Very few individuals were found. A few striated scales lie loose 

 on the type specimen, probably from one of the other species. In 

 the only place in which they lie in situ, they are quite smooth. 

 (Qpr.) 



I. ROSEUS Sowerby. PI. 21, figs. 49, 50. 



Shell ovate-oblong, smooth, roseate ; back rounded ; front valve 

 and lateral areas of the intermediate valves longitudinally, central 

 areas transversely sulcate ; posterior valve with central apex, con- 

 centrically sulcate. Length 17$, breadth 7 2 mill. (Sowb.) 



I. of Plata (Cum ing) ; Fernando Noronha (Challenger Exped.), 

 Peru (Bradley, in Mus. Yale College.) 



Ch. roseus SOWB., P. Z. S. 1832, p. 58; Conch. Illustr., f. 14. 

 REEVE, Conch. Icon., t. 25, f. 119. DESK, in Lam., An. s. Vert., 

 vii, p. 498 (not Chiton roseus Blainville, Diet. Sc. Nat. xxxvi, p. 

 553, 1825, a species of Acanthochiton). Ischnochiton roseus CPU., 

 MS. Ischnochiton boogii HADDON, Chall. Rep., Polyplac., p. 15, 

 (1886.) 



There is not the shadow of an excuse for the change of name made 

 by Haddon, as Blainville's prior G. roseus belongs to a genus uni- 

 versally admitted to be distinct. The west coast locality is doubted 

 by Haddon, but it is supported by specimens in the Yale College 

 collection. 



Carpenter gives the following notes on this species : Valves and 

 plates very thin, subdiaphanous; mucro median, little elevated. 

 Interior: post. v. with 8, central v. 1, ant. v. 11 slits; teeth very 

 acute ; eaves very slender, moderately projecting ; sinus large, flat, 

 high, scarcely laminate ; sutural plates small, subtriangular. Girdle 

 imbricated with minute solid, smooth scales, with bristles intercalated 

 at the margin. The sutural laminae are as small as in Leptochiton, 

 and look like a mere prolongation of the insertion plates round the 

 corner. The scales though normally shaped and arranged, are so 

 minute that Deshayes placed the species in the Tonicioid group. 



Haddon writes of /. roseus (under the name J. boogii), as follows : 



The locality attributed, on the authority of Cuming, to this species, 



made the identification with it of a Chiton from Fernando Noronha 



very doubtful ; a shallow-water species was not likely to live in both 



the Atlantic off Brazil and in the Pacific off' West Columbia, with 



8 



