776 Constitution of some Appendages of the Mollusca, [Auga 
toes thickly coated with feathers, which can be spread out, asi 
by means of the long and straight claws—which may be com- A 
pared with snowshoes—are enabled to run easily over the saom, 4 
the usefulness and the necessity of the lengthening of the sals — 
is self-evident. In the genus Tetrao (=Urogallus+Lyruret 1 
Bonasa) the lateral horny fringes of the toes render the same e 
cellent service, and may fitly be regarded as a kind of snowshows ; 
During the summer this whole outfit becomes superfluous, whid — 
may be the main cause of the periodical shedding.” It mayi — 
this connection be mentioned, that the horny fringes in Tetraone, — l 
and the thick feathering of the toes in Lagopodes mk. a 
during the summer, at which time the toes of the latter at 7 
almost wholly denuded of feathers. 4 
20: a 
ON THE CONSTITUTION OF SOME APPENDAGES OF E 
THE MOLLUSCA. a 
BY W. H. DALL, ’ 
r. is comparatively recently that the organic chemists have de 
voted any time to the investigation of the constitution d 
invertebrate organs or appendages, especially among brachiopods 
and mollusks. In the rare cases in which this has been done thë 
observations in many cases were overlooked by the biologi 
shells of certain brachiopods is almost a singular instance = 
the statement of such a fact has penetrated all the manuals 
text-books. 
The teeth and radula of mollusks, an apparatus 
characteristic of several classes of that sub-kingdom, me 
which classification has been largely based for at least Sa 
years : 
or “horny.” The jaw, which is developed in nearly all of pee 
is referred to in the latest general work on the Mollusks ( Ror 
clopedia Britannica, Art. Mollusca, p. 641), by Professor 
Lankester in the following terms: “ We find a usie 
present in the Glossophora a pair of horny jaws (usually a 
fied) developed as cuticular productions upon the ao 
the lips.” The same author refers to the radula as “a 
band beset with minute teeth,” “a horny cuticular product,” 
a “horny radula or lingual ribbon.” 
