ISCHNOCHITON-CALLISTOCHITON. 87 



the pits varies much. At the sides of the pleura there are generally 

 visible slight forward-converging riblets, pitted where they cross the 

 transverse grooves; and these give a key to the origin of this curious 

 pattern of sculpture. Some black scales are scattered among the 

 reddish ones, on the girdle, and it is besides slightly tessellated with 

 lighter. 



Fig. 64, 65, is drawn from the type specimen (Mus. Smiths. Inst. 

 30946) ; fig. 67 is from a specimen taken at Victoria, B. C., in 15 

 fms., by Mr. C. F. Newcombe. 



I. AUSTRALIS Sowerby. (Vol. XIV, p. 144). PI. 17, figs. 68, 69. 



Young specimens of this species (and adults when not eroded) 

 show a small area at each beak free from longitudinal riblets ; but 

 these riblets are developed upon the ridge toward the forward part 

 of each valve, being finer there than upon the pleura. The lateral 

 areas are generally very coarsely sculptured, as in pi. 17, fig. 68 ; I 

 have seen only one specimen in which the lateral riblets are as fine 

 as in pi. 18, fig. 59 of Vol. XIV. 



Chiton lugubris Gld. (vol. XIV, p. 146), of which the types 

 (Smiths. Inst. Mus., no. 2075) are before me, is merely a young 

 australis, not eroded, and showing conspicuously the smooth, micro- 

 scopically granulate space around each beak. As one of the type 

 specimens is dismembered and the other is curled, I have figured a 

 young australis from the Academy collection to illustrate the form ; 

 the specimen selected being almost exactly like the type. /. lugubris 

 will therefore be added to the synonymy of australis. 



Genus CALLISTOCHITON Cpr. (Vol. XIV, p. 260). 



C. DECORATUS Cpr. PI. 16, fig. 54. (Vol. XIV, p. 269). 



In some specimens of this species the smooth area at the jugal 

 ridge is decidedly narrower than in the typical form, represented on 

 pi. 58, fig. 18 of Vol. XIV, and the lateral ribs are more elevated, 

 acute, and indistinctly granulated, the girdle being tessellated buff 

 and brownish. Central areas buff, lateral areas olivaceous. Poste- 

 rior rib of each valve split by a shallow, small sulcus; and in the 

 individual described (Mus. Smiths. Inst., 58897) there are 12 ribs 

 on the head valve. Surface lusterless. Sculpture of pleura coarser 

 and sharper. 



The differences above noted are presented by a specimen from San 

 Diego, collected by Hemphill. Although the divergence from the 



