REMARKS. vil 
PreLECYPODA, GASTROPODA and CEPHALOPODA, arranged in order from the lowest to 
the highest type. These six principal divisions or classes of the Mollusca are 
generally accepted by the majority of conchologists, (with the exception of the 
CinropopA, the Molluscous characters of which are only very slowly acknowledged). 
Confining ourselves at present to the Gasrropopa, and in a case like the pre- 
sent, when reporting only upon an imperfect local fauna, it would perhaps be a 
great advantage, if we strictly followed some system, which had been adopted and. 
exemplified in any of the leading Manuals of the Mollusca. Itis not, however, easy 
to select from among the numerous systems which have been at various times 
proposed one equally well suited to the zoologist and the palzeontologist. 
In Woodward’s ‘Rudimentary treatise of shells,’ the general classi- 
fication of the Gastroropa is much clearer and more easily understood than in many 
other Conchological works ; and the ways, in which the families are described according 
to their respective relations, appear to be adequate to the state of our yet very im- 
perfect anatomical knowledge of the animals. This treatise is undoubtedly indispen- 
sable for the student of Conchology; still it would at present seem more advisable to 
carry out in the generic nomenclature a more detailed division, than has been 
adopted by Woodward. A similar objection,—if it can be called one,—may be raised. 
against the classification in Philippi’s ‘Handbuch der Conchyliologie,’ 
1853; and still more decidedly against the older systems of Lamarck and others. 
The adoption of smaller and more easily defineable generic groups has, during 
the last few years, been found not only to have increased very considerably our 
specific knowledge of the animals, but it has also most remarkably facilitated the 
study of the Mollusca in general. Many points in morphology and in geographical 
distribution, which would scarcely have had a chance of being so soon cleared up, so 
long as the universal generic denominations such as Cerithiwm, Fusus, Tritonium and 
others remained in use, became at once far more intelligible in consequence of the 
new system of sub-division. Perhaps it would be more correct to say, that the more 
detailed studies of the organization, the habits and the geographical distribution, 
rendered this closer division more a matter of necessity than of mere convenience, 
as it appeared to be at first. Swainson, in hisable ‘Conchology’ (1840), was one 
of the first, who classified in the more recent sense the GASTROPODA into a number 
of characteristic families and sub-families, and he also nearly doubled the then 
existing number of genera. The same course was more systematically pursued by 
Dr. J. H. Gray, especially in his last ‘Catalogue of the Molluscain the 
British Museum’ (1857), and by Henry and Arthur Adams, in their ‘Genera 
