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6. On THE Drvision or CTENOBRANCHOUS GASTEROPODOUS 
Mo.Luvusca INTO LARGER GROUPS AND FAMILIES. 
By Dr. J. E. Gray, F.R.S., V.P.Z.8. erc. 
Cuvier, Dumeril, and Lamarck separated the Gasteropodous Mol- 
lusca with pectinated or comb-like gills, into two divisions, accord- 
ing as they possessed or were without a siphon to facilitate the ad- 
mission of water to their gills, probably being influenced by pre- 
ceding conchologists, who had in a similar marner divided the spiral 
shells into those which had an entire, or an emarginated, or a chan- 
nelled mouth. Lamarck called those with a siphon Zoophaga, and 
those without it Phytophaga, believing the food of the molluscs to 
be indicated by the form of the mantle. As we have become more 
acquainted with the habits of the Mollusca, it has been observed that 
many of the animals without any siphon to the mantle, as Natica, 
Scalaria, Ianthina, &e., are quite as carnivorous as those which have 
the siphon most perfectly developed; on the other hand, Lamarck 
found it requisite to arrange many genera, as Cerithiuwm, Melanopsis, 
Planazis, &e., with the Phytophaga with entire mouths, though the 
animals have as well-developed siphons, and the shells as distinct 
a canal or siphonal notch, as any of the genera of Zoophagous Mol- 
lusca. These divisions, however, have been almost universally 
adopted. Dr. Lovén, in his paper on the Scandinavian Mollusca 
and on the Tongues of these animals, divided the Gasteropoda into 
natural families independent of these divisions, and Dr. Troschel in 
his arrangement of Mollusca has followed the same course, separating 
the families into groups according to the structure of their tongues. 
The observations which Dr. Troschel made on the arrangement which 
I published in Mrs. Gray’s work, ‘ Figures of Molluscous Animals,’ 
have induced me to reconsider the subject, consult again all the 
authorities, and examine the tongues of the molluscous animals which 
have been lately received at the Museum collections. 
Being impressed with the importance which Dr. Lovén attached to 
the form of the mouth, I was induced to pay attention to this charac- 
ter, and I believe that it affords a much more natural means of sepa- 
rating the families into two great groups, than the presence or absence 
of the siphon of the mantle, and one which appears to be more con- 
sistent with the habits of the animal and much less liable to excep- 
tions. I may observe in passing, that some of the French zoologists 
do not appear to have been impressed with its importance, for MM. 
Quoy and Gaimard in some few instances erroneously represent some 
of the species of a genus, a Murex and Terebra for example, as 
having a rostrum, while the greater part of the species are properly 
represented without it, and as having a proboscis; and the same may ~- 
be remarked of some of the more modern figures of these animals, 
I fully expect that many naturalists, especially those who have 
chiefly confined their studies to the external form of the shell or to the 
fossil species, will consider that the system here proposed is very 
artificial, as it separates from one another many genera and families 
which they have regarded as being very nearly allied, or as belonging 
