284 PROCEEDINGS OF UNITED STATES NATIONAL MUSUEM. 



C. LOPHYROIDEA. 



lusertion plates broad, pectinated, projecting backward. 



25. Chiton Linn<5. 



a. Kadsia Gray. 



26. Tonivia Gray. 



a. Fannettia Dall. 



27. Eitdoxochifon Shuttleworth. 



28. Craspedochiton Sbuttleworth, 



D. ACANTHOIDEA. 



Insertion plates thrown forward. 



♦Plates broad, pectinated {A. lophyroidea). 



29. Sclerochiton Cpr. | 



** Plates sharp, grooved outside {A. typica). 



30. Acanlhopleura Guilding. 



a. Lueilina Dall. 



b. Corepliium Gray. 



c. Francisia Cpr. 



***Plates sharp, smooth (,A. ischnoidea.) 



31. Dinoplax Cpr. 



32. Midden dor fia Cpr. 



a. Beanella Dall. 



33. Nultallina Cpr. 



34. Arihiiria Cpr. 



35. PhaceUopleura Guilding. 



Section II. — Ohitones irregulares. 

 Tail plate abnormal or with a sinus behind. 



E. SCHIZOIDEA. 



Tail valve fissured. 



36. Lorica H. and A. Adams. I 37. ScMzochiton Gray. 



a. Aulacochiton (Sbuttleworth) Cpr. | 



F. Placiphoroidea. 

 Tail valve unslit, internally ridged, mucro nearly terminal. 



38. Fnoplochifon Gray. 



39. Ornithochiton Gray. 



40. Placiphora Gray. 



a. Fremhli/a H. Adams. 



b. Euplaciphora Shuttleworth. 



c. Guilding ia Cpr. 



G. MOPALOIDEA. 



Tail valve with posterior sinus and one slit on each side. 



41. Mopalia Gray. 



a. Placiphorella Ct^t. 



42. Katherina Gray. 



43. Acanthochiton (Leach) Herrm. 



a. Macandrellus Cpr. 



b. Stectoplax Cpr. 



44. Notoplax H. Adams. 



