THE NAUTILUS. 



VOL. x. SEPTEMBER, 1896. No. 5 



NOTES ON SOME WEST AMERICAN CHITONS 



];Y H A. PILSBKY. 



I. 



Among some interesting small Chitons from San Pedro, Califor- 

 nia, collected by Mr. T. S. Oldroyd, which I have lately examined 

 (through the kindness of Dr. Dull), the following call for especial 

 notice, as they otter difference!! from the types figured in the Manual 

 of Conchology. 



Mopalia imporcata Cpr. 



The single specimen measures 9 by 18J mm., and is somewhat 

 more elevated than the type of the species; color pale olivaceous, 

 white towards the girdle, speckled on the ribs of lateral areas with 

 brown, and with a brown patch on each pleural tract. The teeth 

 are very distinctly thickened along the outer edges of the slits, as in 

 the typical Callistochitons. Sculpture typical. 



The color is different from that of the type, and the specimen is 

 larger. 



Ischnoohiton scabricostatus Cpr. 



Lateral areas with four (on one side of valve ii, five ; on one side 

 of valves iv and v, three) radial riblets, which are very weakly 

 hardly perceptibly, granose. Sutures very feebly crenate. Anterior 

 and posterior valves with 9 slits each. Color reddish (but not at 



all of an orange cast), with a few inconspicuous white spots on 



some of the lateral areas. 



