PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 299 



Eatherina Gray. 



K. tunicata Wood. (Type. ) Minor lateral thin aud coalescent with the inner wing 

 above, outer wing small ; major lateral normal, tridentate ; imcini ridged or knobby, 

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



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



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

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

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



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

 much as in the last. Fig. 39. 



Macandrellus Cpr. (Type M. costatuft, Ad. & Aug.) 



M. costatusf Ad. & Augas. Like Acanthochiton avicula, but the shaft of the major 

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

 Stectoplax and Kotoplax not examined. 



Cryptoidea. 

 Cryptoconchus Blainv. 



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

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

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



Amicula Gray. {= Symmetrogejjhyrus Midd., StimpsonieUa Cpr.) 



A. vestita Shy. = Emersonii Couth. Gld. (Type.) Minor lateral bi-alate, normal ; 

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

 ward to the radula, formiug a vaulted hollow arch beneath the upper part of the 

 shaft ; major uncinus aborted. Fig. 43. « 



A. Pallasii Midd. (Type of Syvimetrogephyrus.) 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. 



Chlamydochiton not examined. 



Cr3rptochiton Midd. Gray. 



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

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

 cinus aborted. Fig. 44. 



Chitonellus Blainville. 



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

 major lateral normal, tridentate with a plain shaft; uncini more or less ridged, major 

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



It will be seen that Gray's figure (here reproduced) is very eiToneous, and seems^ 

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



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

 Choneplax, Chilonincun, and CryptopJax not examined. 



Nomenclature. — The noinenclatiue of Chitons has suffered greatly 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 heen fruitful of difficulty 5 the Messrs. H. and 



