296 PEOCEEDINGS OP UNITED STATES NATIONAL MUSEUM. 



Tonicella Carpenter. (Type T. marmorea Fabr.) 



'' T. Uneaia Wood. Minor lateral witli a loug shaft, bi-alate, normal ; major lateral 

 with two small denticles on the inner side of the cusp and one large outer denticle, 

 shaft normal; major uncinus spatulate, normal. Fig. 5. 



T. marmorea Fabr. As in the last, but with only one small inner denticle on tho 

 cusp of the major lateral. Fig. 6. 



T. submarmorea Midd. Minor lateral shaped like a jdoughshare ; other teeth much 

 as in the last. Fig. 7. 



Schizoplax Dall. 



S. Brandtii Midd. (Type.) Minor lateral a broad shaft with a simple cusp, base 

 with a groove or sinus, no wings; major lateral tridcntate. Fig. 8. 

 Leptoplax not examined. 



Chaetopleura Shuttleworth. (Type C. Peruviana Lam.) 



C. (jemmaC\>v. Ehachidiau tooth broad and short; minor lateral normal, outer 

 wing inconspicuous; major lateral tridentate, shaft keeled, keel with a small elon- 

 gate cuspidate process. Fig. 9. 



? C. Hartmegii Cpr. Minor lateral reduced to a broad cusped shaft with a remnant 

 of an inner wing and a thickened base; major lateral tridentate, with no keel or pro- 

 cess, shaft normal. Fig. 10. 



Maugerella Cpr. 



M. conspicua Cpr. (Type. ) Minor lateral bi-alafce, top of inner wing and shaft bent 

 into a twisted cusp Avith a small process extending outward from the apex of the 

 shaft; major lateral tridentate, shaft with a keel and cuspidate process. Fig. 11. 



Spongiochiton not examined. 



ISCHNOCHITONS. 

 Hcterozona not examined. 

 Stenoradsia Cpr. 



S. magdalenensis JlmAs,. (Type.) Shaft of minor lateral with a cusp and process, 

 inner wing normal, outer wing inconspicuous; major lateral tridentate, with a keel 

 and cuspidate process on the front of the shaft. Fig. 12. 



Stenoplax Cpr. 



S. limaciformis Shj. (Type.) Rhachidian tooth very small ; minor lateral normal, 

 shaft with a minute hook at the apex; major lateral with a simple cusp, shaft bear- 

 ing a keel and cuspidate process; major uncinus very small. Fig. 13. 



IschnopIa:s Cpr. 



/. 2)C(:tiitatu>i Sl>y. (Ty^ie.) Minor lateral with broad, stout, cusped shaft, inner 

 wing expanded, outer wing reduced to a rudiment, with a liuguiform process; major 

 lateral with a simple rounded cusp, shaft with a triangular keel but no i^rojecting 

 jjrocess. Fig. 23. 



Ischnochiton Cpr. ex Gray. (Type /. Jomjicymlm Quoy.) 



/. cooperi Cpr. Minor lateral with the outer wing reduced to a button near the 

 cusp of the shaft, inner wing small; major lateral with simple cusp, shaft Avith a 

 keel, bearing a cuspidate process; major uncinus broad, spatulate, thicker near the 

 edges. Fig. 1.5. 



/. inlerstinctus Gld. Minor lateral composed of a shaft with large, twisted, hooked 

 cusp, and possessing only slight rudiments of wings; major lateral tridentate, keeled 

 on tho shaft, with a si)atulate process on the keel; uncini rugose, major uncinus 

 sharply bent, strengthened by narrow ridges on the spatulate cusp. Fig. 16. 



J. regularis Cpr. Teeth closely resembling those of I. Cooperi, but nunor lateral 

 with a small outer wing. Fijj. 14. 



