46 SCHIZOPLAX. 



Var. NUTTALLII Cpr. 



Umbo flatter ; valves broad, non-swelling, squared at the sides, 

 and not beaked or waved. Posterior valve having 11, central 1, 

 anterior 8 slits. 



Habitat same as hartwegii. 



Chiton nuttallii CPR. P. Z. S. 1855, p. 231 ; Trachydermon n., 

 CPR. Suppl. Rep. B. Asso. 1863, p. 649 ; Chcetopleura n., CPR. MS., 

 in Dall, Proc. U. S. Nat. Mus. 1878, p. 330. 



I am unable to separate this form from hartwegii, as transition 

 specimens are numerous. 



T. BIPUNCTATA Sowerby. PL 14, fig. 90. 



Shell ovate, smooth ; green, variegated with black and white ; 

 margin concolored, generally having a white spot on each side 

 between the first and second valves, marginal ligament smooth. 

 Length 12, breadth 61 mill. (Sowb.) 



Inner Lobos Island, Pern, under stones at low water. 



C. bipunctatus SOWB. P. Z. S. 1832, p. 104 ; Couch, lllustr. f. 27. 



This species varies much in coloring, some specimens being nearly 

 black, others light green, and some much and prettily varied. In 

 almost all a white mark may be observed on the margin just 

 behind the anterior valve. (Sowb.} 



Carpenter's notes on the types are as follows : Posterior valve 

 having 9, central 1, anterior valve 9 slits ; teeth smooth, stumpy ; 

 eaves very short, spongy. Girdle smooth with extremely short, 

 scattered hairs, and two white spots at the sutures of anterior valve. 

 Valves beaked, but they seem to have no pattern of sculpture, only 

 a very close quincunx (arrangement of granules). Looks like 

 a Trachydermon without scales. The mucro is in front of the 

 middle, the slope behind it concave. Color greenish, generally 

 with a white blotch behind. 



Length 12, breadth 7 mill. 



Congeneric with and very like a small nuttallii. 



Genus IX. SCHIZOPLAX Dall, 1878. 



Schizoplax DALL, Proc. U. S. Hat. Mus. p. 2, Jan., 1878 ; 1. c. p. 

 328. CPR. MS. Type Chiton brandtii Midd. 



Shell and girdle as in Tonicella, except that the median valves 

 have a central jugal slit filled with cartilage, narrower in front; 



