342 CHITONIDiE. 



ISCHNOCHITON (restricted). Scales transverse, flattened, some- 

 what imbricated, generall}^ striated. 



ISCHNORADSIA, Cpr. (ex Shuttlew.). Scales striated ; central 

 valves with many slits. G. Irifidus^ Cpr. 



LEPIDOPLEURUS, Cpr. Scales solid, imbricated, smooth. G. 

 Mertensii^ Cpr. 



LEPIDORADSIA, Cpr. Similar to the last, with man}'- slits in 

 central valves. G. Australis, Sowb. 



STENOPLAX, Cpr. Body elongate; scales elongate, chafTy, 

 striated, irregular and crowded. G. limaciformis, Sowb. 

 (Ixxxv, 96). 



STENORADSiA, Cpr. Like Stenoplax, with numerous side-slits. 

 G. Magdalensis, Hinds (Ixxxv, T*!). 



ISCHNOPLAX, Cpr. Like Stenoplax, but with occasional large 

 scales rising above the rest, and a multitude of short striated 

 bristles ; mucro raised, subposterior. 



HETEROZONA, Carpenter. Body elongate ; two kinds of rather, 

 solid, striated scales. 



CALLiSTOCHiTON, Cpr. Insertion-plates regular, branching ; 

 middle valve with one, anterior and posterior with many slits ; 

 teeth excurved, plumate ; eaves projecting, long ; sinus broad, 

 shallow, laminate ; girdle narrow, with small scales ; gills 

 encircling. 



* * With girdle-pores. 



CALLiSTOPLAX, Cpr. Shell as in Callistochiton, poriferous girdle 

 naked. G. retusui<, Sowb. (Ixxxv, 78). 



ANGASiA, Cpr. (Hanlejda, Ad. and Angas, not Gray.) Shell like 

 Chastopleura, but the eaves small ; girdle minutely squamulose- 

 pilose, fasciculated at the sutures. A. tetrica., Cpr. 



NEWCOMBiA, Cpr. Insertion-plates regular, branching ; middle 

 valve with one, anterior and posterior with manj^ slits ; teeth 

 solid, not propped ; eaves short ; sinus rounded, simple; girdle 

 fleshy, with long, hairy bristles. 



CERATOZONA, Dall. Shell like Chaetopleura, but the teeth raised,' 

 eaves short ; girdle smooth, fasciculated around the sutures and 

 margin. This diff'ers from all other hairy or spiny Chitons, at 

 all nearly related to it, in the mantle-ornaments not being 

 inserted into sockets, but being extensions of its surface. G. 

 Giiildingii, Reeve (Ixxxv, 19). 



PALLOCHITON, Dall. Like Nuttallina ; zone downy ; central 

 laminae unifissured. This section unites in a form resembling 

 Xuttallina, some of the features of Middendorfia, from which the 

 girdle diflfers in being spongy and covered with soft hairs 

 instead of short shelly bristles. 0. lanuginosus, Cpr. 



C. Lophyroidea. 

 Insertion-plates broad, pectinated, projecting backward. 



