PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 299 



Katherina Gray. 



K. titnicata Wood. (Typo. ) Minor lateral tliin and coalescent witli tlio inner wi^ 

 above, outer wing small ; major lateral normal, tridentato ; uncini ridged or knobby, 

 except major uncinus, which is elongate and narrow. Fig. 37. 



Acanthochiton Herrm. ex Leach. (Type A. fascicularis Auct.) 



A. avicula Cpr. Minor lateral with the shaft branched at base, leaf-shaped ; major 

 lateral with trideutate cusp ; shaft with triangular keel, of which the tip is bent 

 outward ; major nncinus short, normal. Fig. 38. 



A. splculosns Rve. Minor lateral normal, bi-alate; major lateral and other teeth 

 nuich as in the last. Fig. 39. 



Macaiidrellus Cpr. (Type M. coHiaius, Ad. «fc Ang.) 



M. costatusf Ad. & Angas. Like AcantliocUtoii avicula, but the shaft of the major 

 lateral normal without a keel. Fig. 40. Specimen from Port Jackson, Australia. 

 Stectojjlax and Notoplax not examined. 



Cryptoidea. 

 Cryptoconchus Blainv. 



C. monlicularis Quoy. (Type. ) Minor lateral normal, leaf-shaped, base geniculate ; 

 major lateral with trideutate cusp and plain normal shaft ; a rugosity on the second 

 uncinus projecting inward over the first; major uncinus slender, short. Fig. 41. 



Amicula Gray. (== Symmetrogephyrus Midd., Stimpsoniella Cpr. ) 



A. vestita Sby. = Emersonii Couth. Gld. (Tyjie. ) Minor lateral bi-alate, norm.al ; 

 major lateral trideutate, with plain shaft, whose lateral expansions are bent back- 

 ward to the radula, forming a vaulted hollo^y arch beneath the upper part of the 

 shaft ; major uucinus aborted. Fig. 43. 



A. Pallasii Midd. (TjT)e of Symmetrogephyrus.) As in the last, except that the 

 sides of the major lateral are bent forward, and the major uncinus is present and 

 normal. Fig. 42. 



ChlamydocMton not examined. 



Cryptochiton Midd. Gray. 



C. Stelleri Midd. (Type.) Minor lateral normal, leaf-shaped ; major lateral with 

 trideutate cusp and a small keel on the shaft; inner two uucini ridged, major un- 

 cinus aborted. Fig. 44. 



Chitonellus Blainville. 



C. fasciatus Quoy. (Tyjie.) Minor lateral bi-alate, with a strongly curved shaft; 

 major lateral normal, trideutate with a plain shaft; uncini more gr less ridged, major 

 uncinus nearly straight, long, slender, spatulate. Fig. 45, 45 a. 



It will be seen that Gray's tigure (here reproduced) is very erroneous, and seems 

 to have been taken from the immature end of the radula. 



Fig. D.— Teeth of Chitonellus, after Gray. 

 CJioneplax, Chitoniscus, and CryptopJax not examined. 



Nomenclature. — The nomenclatm^e of Chitons has suffered gTeatly from 

 neglect of various writers to specify or adopt types of the genera they 

 proposed or used. The neglect of internal characters in assorting spe- 

 cies into genera has also been fruitful of difiaculty; the Messrs. H. and 



