XXV. 
CLASS SCAPHOPODA. 
Dentaliide. 
Dentalium, L. 
(typical example D. elephantinum, L.) 
D. vulgare, Da Costa(=Tarentinum, 
Lam.) 
D. entalis, L. 
D. striolatum, Stimpson ( = abys- 
sorum, Sars.) 
Siphodentalium, Sars, 1849. 
S. lofotense, Sars. 
Cadulus, Philippi, 1844, 
C. subfusiformis, Sars. 
C, Jeffreysi, Monterosato. 
The classification of the Pelecypoda (frequently called also 
Lamelli branchiata) is a subject to which much attention has been 
given, especially by continental malacologists, but with results which, 
as yet, can hardly be called thoroughly satisfactory. Various schemes 
have been tried, of which, perhaps, the most familiar to British 
collectors (from its having been followed by Gwyn Jeffreys) is that 
founded on the presence or absence of siphons. This was proposed 
by D’Orkbigny, but has now been generally abandoned, and 
we are chiefly concerned with that of Fischer, extended and re- 
written by Pelseneer, and that of Neumayer and Dall. By this 
it is not intended to imply that the systems of Fischer and Pelseneer, 
Neumayer and Dall, are respectively identical, but merely that they 
are founded on similar lines. The former are malacological, founded 
on the structure of the gills, the latter conchological, founded on 
the characters of the hinge. While admitting in favour of these 
last characters that their great value in classifying fossils renders 
them of perhaps greatergeneral applicability, still they appear to have 
as yet nct been sufficiently tested, and the most satisfactory course, in 
