208 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



ACANTIIOLDEA. 



Sclcrochiton, Francisia, Dinoplax, Dawsonia, Beania, and Arthuria not examined, 

 Acanthopleura Cpr. ex Guilding. 



A. spiniyera Sby. (Type.) Minor lateral large, shaft long, cusped, wings long, 

 narrow, linguiform; major lateral with a simple rounded cusp, shaft keeled, keel 

 with a cuspidate process; inner uncini nodulose; major uncinus short, broad, thick. 

 Fig. 28. 



Lucia Gld. 



L. confossa Gld. (Type.) Minor lateral twisted, peculiar, outer wing broad, re- 

 curved at tip, inner wing small, strengthened by a branch from the shaft (Fig. 29a) ; 

 rhachidian* minute ; major lateral with a quadridentatc cusp, shaft with its inner 

 expansion terminating in a cuspidate process above ; inner two uncini ridged ; major 

 uncinus feather-shaped, vane on the inner edge (29&). Fig. 29. 



Corephium Gray (not Brown). 



C. echinatum Sby. (Type. ) Minor lateral with the shaft expanded above, with a 

 cusp confluent with the upper edge of the small inner wing, outer wing small; 

 major lateral with a rounded tridentate black-margined cusp bearing a spot on the 

 middle denticle, shaft keeled in front, keel produced into a thin liuguiform process; 

 major uncinus asymmetrical, somewhat spoon-shaped. Fig. 30. 



Nuttallina Cpr. 



JSf. scabra Eve. (Type.) Minor lateral normal, bi-alate; major lateral normal, 

 with plain shaft and tridentate cusp; major uncinus long, slender, with small ex- 

 pansion at the tip. Fig. 31. 



Phacellopleura Cpr. ex Guilding. 



P. porphyritica Rve. sp. unica. Minor lateral with an inner but no outer wing, 

 otherwise normal ; major lateral normal, with plain shaft and tridentate cusp; inner 

 uncini nodulose ; major uncinus normal, simulate.' Fig. 32. 



B. — IRREGULAR CHITONS. 

 Schizoidea. 



I have not been able to obtain the radula of any of the few species comprised in 

 the genera Lorica, Aulacocliiton, Schizochiton, Fnoplockiton, and Onithochiton. 



Placipiioroidea. 



Placiphora Cpr. ex Gray. 



P. Carmichaelis Gray (=*C. setiyer King and Fremblyi Brod.). Type. Rhachidian 

 tooth with its edges folded inward. Minor lateral with a large narrow inner wing, 

 small outer wing, and a median keel on the slender shaft; major lateral with a largo 

 tridentate cusp, shaft slender, normal; major uncinus with a small expansion at 

 the tip. Fig. 33. 



Euplacipliora, Fremblyia (= Streptochiton Cpr.), and Guildingia not examined. 



MOPALOIDEA. 



Mopalia Cpr. ex Gray. 



M. ciliata Sby. (Type, = muscosa Gld. -f Hindsii Gray.) Minor lateral normal, 

 bi-alate; major lateral normal, tridentate with a plain shaft; inner two uncini 

 ridged; major uncinus rather short, normal. Fig. 35, 35 a. 



M. JVossncssenskii Midd. (Kennerlyi Cpr.). Similar to the last with a longer major 

 uncinus. Fig. 34. 



Placiphorella Cpr. 



P.velata Cpr. (Type.) Rhachidian very largo; minor lateral unusually small, 

 both normal ; major lateral tridentate, normal. Fig. 30, 30 a. 



