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 Leidy (Terr. Moll. U. S., 1, p. 250, pl. 3, 1851) in de- 
scribing the anatomy of Tebennophorus, did not mention finding 
a rudimentary shell. W. G. Binney (Terr. Moll. U. 8., 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 Philomycina, in which he places the genus Philomycus, 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 carolinianus (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 Pallifera 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- 
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