86 THE NAUTILUS. 



Tebennophorus, signifying "wearing a cloak". In diagnosing 

 the genus, Binney states that it is "without testaceous rudi- 

 ment". Wyman (Bost. Journ. Nat. Hist., 4, p. 411, 1844) 

 and Leicly (Terr. Moll. U. S., 1, p. 250, pi. 3, 1851) in de- 

 scribing the anatomy of Tebennophorus, did not mention finding 

 a rudimentary shell. W. G. Binney (Terr. Moll. U. S., 5, p. 

 179, 1878) specifies that Tebennophorus has no external or in- 

 ternal shell, and adds (p. 180) that " the internal, rudimentary, 

 nail like shell, described by Dr. Gray, has not been noticed by 

 any American author". Dr. Gray's description (Cat. Pulmon. 

 Brit. Mus. , part 1, p. 158, 1855) of the genus Philomycus, in- 

 cludes the statement, "Shell minute, nail like, concealed in the 

 front part of the mantle". Yet (p. 155) in describing the 

 tribe Philomydna, in which he places the genus Phttomycus, he 

 states, "Shell none". From Dr. Gray's description of the 

 shell as being " nail-like", and "concealed in the front part of 

 the mantle", I doubt that he had the shell of Philomycus caro- 

 linianus. 



An examination of the jaw and radula of each of the speci- 

 mens in which a shell was found, disclosed the fact that the 

 jaw varies considerably in specimens apparently otherwise 

 identical. In the fifteen specimens from Hudson, Ohio (M. C. 

 Z. 48211), which I consider typical mrolinianus (Bosc), as de- 

 scribed by Binney, thirteen possessed a smooth jaw, with very 

 faint longitudinal and transverse striae showing only when 

 highly magnified. The remaining two were strongly plaited 

 (figs. 2, 3). Of the three specimens (M. C. Z. 48211 H) sepa- 

 rated from the others because of the reddish tinge of the mantle, 

 the jaw of one was similar to fig. 2, the others were smooth. 

 This plaiting of the jaw, although it may be felt with a fine 

 needle, is not to be confused with the ribbing of the jaw as seen 

 in Palli/era dorsalis Binney (Morse, Journ. Port. Soc. Nat. 

 Hist., 1, p. 8, f. 5, 1864). That portion of the mouth which 

 carries the jaw in Philomycus carolinianus, is always deeply fur- 

 rowed, and it appears that these furrows may, or may not leave 

 their impression upon the jaw. It is possible that the presence 

 or absence of plaiting in the jaw may be entirely a question of 

 age. In all of the specimens examined none of the other char- 



