284 PROCEEDINGS OF UNITED STATES NATIONAL MUSUEM. 



0. LOPHYROIDEA. 



lusertion plates broad, pectinated, projecting backward. 



25. Chiton Liun^. 



a. Eadsia Gray. 



26. Tonida Gray. 



a. Fannettia Dall. 



27. Eudoxorhifon Shnttleworth. 



28. Craspedochiton Sbuttlewortb. 



D. xlCANTHOIDEA. 



Insertion plates thrown forward. 



* Plates broad, i^ectinated {A. lophyroidea). 



29. ScJerochifon Cpr. | 



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



30. Acanihopleura Guilding. 



a. Lucilina Dall. 

 h. Corephium Gray, 

 c. Francisia Cpr. 



31. Dinoplax Cpr. 



32. Middendorfia Cpr. 



a. Beanella Dall. 



''Plates sharp, smooth [A. ischnoidea.) 



33. NuitalUna Cpr. 



34. Arthuria Cpr. 

 3.5. Phacellopleura Guilding. 



Section II. — Chitones irregulares. 

 Tail plate abnormal or with a sinus behind. 



E. SCHIZOIDEA. 



Tail valve fissured. 



36, Lonca H. and A. Adams. [ 37. Schizocliiton Gray. 



a. Aulacochiton (Sliuttleworth) Cpr. | 



F. Placiphoroidea. 

 Tail valve unslit, internally ridged, mucro nearly terminal. 



38. Enoplochiton Gray. I 40. Placiphora Gray. 



39. Ornithochiton Gray. | a. Frembh/a H. Adams. 



I b, Euplacipliora Sbuttlewortb. 



1 c. Guildingia Cpr. 



G. MOPALOIDEA. 



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



41. Mopalia Gray. 



a. PlaciphoreUa Cpr. 



42. Katherina Gray. 



43. Aeanfhochitoti (Leacb) Herrm. 



a. Macaiidrellus Cpr. 



b. Stectoplax Cpr. 



44. Notoplax H. Adams. 



