244: CRETACEOUS GASTROPODA 
XXVI. Family,—SILIQUARITD A. 
Chenu (Man., p. 321) introduced this family for the shells known as Siliquaria, 
and we believe, that it ought to be accepted. Some conchologists follow Gray’s 
classification in retaining the sub-family szzzqvarrrva in the Varueripz; others 
do not think even this division necessary, and admit only one genus, either under the 
name Siliquaria or Tenagodus. 
When we regard the distinctions between Pravroromaripxz and Trocuips 
sufficiently important, to form the basis of two families, it appears to us fully justi- 
fiable to make a similar separation between the Vzruxrrz and the Srzrevarups. 
The existence of a slit in the mantle of the animal and in the shell, being a canal 
through which the water is supplied to the branchial plume, seems to be of much 
sveater importance, than, for instance, is the length of the tentacles and eye-pedi- 
cles ; or whether the position of the nucleus of the operculum is apical or lateral. 
Mérch in his “‘ Review of the genus Tenagodus” (Proceed. Zool. Soc., Lond., 1860, 
p- 400, ete.) admits four sub-genera— 
1. <Agathirses, Montfort, 1810, which includes chiefly fossil species, and is 
characterized by the band being composed of numerous, isolated holes. 
2. Tenagodus, Guettard, 1774, (Morch, 1. cit., p. 402). 
3. Siliquarius, Montfort, 1810, (Mérch, 1. cit., p. 4038). 
4. Pyzxipoma, Mérch, 1860, 1. cit., p. 409. 
‘T am much inclined to regard the sub-genera as of generic value,’ says Mérch, 
(1. cit., p. 412), in which we fully concur with that author. We do not see any 
reason, why characters, upon which genera like Plewrotomaria, Ditremaria, Poly- 
tremaria, Trochotoma, and others have been established, should prove perfectly value- 
less in the classification of the Szzrgvuarup#. Moreover we believe, that the dis- 
tinctions of genera will be carried still farther than is now proposed, when we 
come to know more of the fossil species, and of the animals of the recent shells. 
More recently (Journ. de Conch., Paris, 1865, Ser. III, Vol. V, p. 18), Mérch 
says, “il me parait probable que le tube du Cryptobia Michelini est construit 
par un Mollusque voisin des Tenagodus et surtout du sous-genre spongicole Pyxi- 
poma.” The genus Cryptobia of Deshayes will, therefore, probably have to be added 
to this family. 
There are about twenty tertiary fossil species known, and Deshayes (Anm. s. 
vert. bas. de Paris, Vol. II, p. 292), says that one species had been mentioned from 
the upper cretaceous beds of Taxoe in Norway. I am not acquainted with this 
or any other secondary species of the SzzrqvariuD2#. 
