J. D. MACDONALD ON THE CLASSIFICATION OF THE GASTEROPODA. 73 



General Classification of the Gasteropoda. 



I am thus insensibly led into the subject of classification, which I must say I approach 

 with considerable diffidence, being fully conscious of the danger of falling into a dictatorial 

 style, where the results of my ovm researches are at variance with the views of manj 

 worthy cultivators of the science of Malacology. It is quite foreign to my present pur- 

 pose to enter upon the analysis of any single system. Well-informed zoologists naturally 

 make what they believe to be truthful selections from all available systems, and thus, as it 

 were, compound their own creed ; hence I have to deal rather with such matters as ar e 

 generally accepted than wdth the tenets of particular men. In justice to Mr. S. P. Wood- 

 ward, I do not hesitate to state that the soundest general work on the Mollusca that has 

 hitherto appeared in England is his little Manual published by Weale. There is more 

 nature, truth, and judicious conciseness in all the descriptive parts than one is accustomed 

 to meet with in works of this kind ; and, although I am sometimes at issue with him, 1 

 trust that my opposition is never factious or merely for victory's sake. 



Mr. Woodward has availed himself of the characters aflForded by the lingual dentition 

 more extensively, I believe, than any previous writer, if we except Professor Loven ; 

 but much remains to be done before these can be successfully applied in the defining of 

 the natural families, and still more before all the genera of Gasteropods can be referred to 

 their proper places in the system. In the following Table, sho^ving the general nature 

 of the lingual dentition and of the auditory concretions in the principal families, I have 

 merely endeavoured to make a step in the right direction ; though I have little doubt 

 that when the numerous errors which are always incident to attempts embracing so wide 

 a scope shall have been cleared away, and the right exposition given of the value and 

 bearing of assumed points of affinity, a system mil result inferior to none in the whole 

 department of Zoology in the truthfulness of its natural arrangement. 



From more extended study of the sul)ject, since my former paper on the materials of 

 classification was written, I have arrived at the conclusion that the nature of the contents 

 of the auditory sacs is of minor importance to the primary characters of tlie lingual den- 

 tition, as to whether it is elongated and strap-like, or broad and pavimental. Two cir- 

 cumstances in particular suggest this view, viz. : — 1st. The close anatomical relationship 

 existing between Cerithmm and Planaxis, and even the almost actual similarity of their 

 lingual teeth, although the auditory sacs in the former contain otoconia and in the latter 

 spherical otoliths. 2ndly. Several of the Eolidce (if I am not mistaken, I think I may 

 venture to add the genus Flabellina) have otoconial particles, while the others in general 

 have otoliths. It cannot be supposed, however, on this account that the few belong to a 

 different family; for their whole anatomy refutes such a supposition. 



I may remark that amongst the Boridce also I have observed the occasional occurrence 

 of minute otoliths instead- of otoconia. It is worthy of note that the otoliths, wherever 

 they occur in such families as usually present otoconia, are exceedingly small, like the 

 single primordial otoconial particle of the young Fteropod or Nudibraitch ; and in the 

 converse examples, as in the Cerithiidce, where the presence of otoconia might a priori 

 be quite unexpected, they are, as a rule, both few and large. 



VOL. XXIII. li 



