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IV. On the Lingual Dentition of some West-Indian Gasteropoda. 

 By R. J. Lechmere Gtippy, Esq., F.G.S., and Jabez Hogg, Esq., F.L.S., 3LB.C.S.L. 8f 



(Plate XI.) 



Read June 21st, 1866. 



SINCE the investigations of Loven into the lingual dentition of the glossophorous 

 Mollusca, various observers have studied the subject, with great advantage to our know- 

 ledge of the affinities of those animals. Thus we find, amongst other changes, that it 

 has been necessary to remove the Proserpinadae from the neighbourhood of the Cyclo- 

 phoridae, to which they were formerly supposed to be nearly related, and to place them 

 in a more natural position near the Neritidee. That these investigations are of great 

 value is also shown by the light which has been shed on the true position of Aporrhais, 

 supposed by so great a naturalist as Professor Eorbes to be akin to the Cerithiidse, but 

 which is shown by its dentition to belong to the Strombidse. When once we have thus 

 ascertained the natural position of a genus whose relations are otherwise somewhat 

 doubtful, it is surprising how the characters of the shell, perhaps misunderstood before, 

 concur to bear out the affinities indicated by the teeth. Thus the young Aporrhais 

 resembles a young S trombus or Mostellaria ; and Ceres and Proserpina have evidently 

 characters which approach them to Nerita. Observations on Helicina, published in 

 1864, by one of the authors, showed the relationship of that genus to Nerita, to which 

 indeed in its dentition it bears a stronger resemblance than does even Ceres. These 



views have been confirmed, independently, by several authors. 



It is our object, in the present paper, to make known some new forms of lingual denti- 

 tion, some of which, it will be observed, point the way to further reforms in our classifi- 

 cation of the Gasteropoda *. 



* Dr. J. Gray, F.R.S. ('Annals of Natural History,' ser. 2, vol. x. p. 413), writes : — "One result of the study of 

 these papers (Love'n's "On the Tongues of Mollusca") and the examination of the tongues of several mollusks has 

 heen to establish more firmly the theory which I have long entertained, that no species of gasteropodous molluscous 

 animal can be proj rly placed in the system unless we are enabled to examine the animal, the shell, the operculum, 

 and the structure of its tongue; and as none of these parts but the shell can be examined in the fossil species, their 

 position in the various genera must be always attended with more or less uncertainty." 



Professor Huxley very properly objects to the use of the commonly-accepted term tongue for the tooth-bearing 

 membrane of the mollusca, and he appropriately designates it " the odontophore." 



" The odontophore consists essentially of a cartilaginous strap, which bears a long series of transversely-disposed 

 teeth. The ends of the strap are connected with muscles attached to the upper and lower surface of the hinder ex- 

 tremities of the cartilaginous cushion ; and these muscles, by their alternate contractions, cause the toothed strap 

 to work, backwards and forwards, over the end of the pulley formed by its anterior end. The strap consequently acts 

 after the fashion of a chain-saw (rather of a r#s/>?)upon any substance to which it is applied ; and the resulting wear 

 and tear of its anterior teeth are made good by the incessant development of new teeth in the secreting sac in which 

 the hinder end of the strap is lodged. Besides the chainsaw-like motion of the strap, the odontophore may be capable 

 of a licking or scraping action as a whole/' — Huxley s Elements of Comparative Anatomy, p. 36, 



VOL. XXVI. 



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