528 MR. B. B. WOODWARD ON THE GROWTH AND [JuDC 14, 



7. On the Mode of Growth and the Structure of the Shell in 

 Velates conoideus, Lamk.^ and other Neritidce. By B. B. 

 Woodward, F.G.S., F.R.M.S. (Communicated by 

 Prof. Flower, C.B., President.) 



[Eeceived June 7, 1892.] 



(Plates XXXI. & XXXII.) 



At the June meeting of this Society in 1889 attention was drawn 

 by the writer to the very peculiar method of growth of the shell which 

 forms the principal subject of this communication, as was shown 

 by sections of specimens then exhibited. Unfortunately a far too 

 prevalent epidemic interfered for the time with further investigation, 

 which on being resumed has lead to more extended inquiry than at 

 first contemplated, with results, however, which it is hoped may 

 prove to be of some interest. The species was then spoken of as 

 Neritina schmideliana ; but on reference to the literature it appears 

 that this name cannot stand, since Chemnitz's description ' was pub- 

 lished prior to the adoption, in the ' Conchylien-Cabinet,' of the 

 binomial system of nomenclature. The next name in order of priority 

 was that conferred by Gmelin in his edition of Linne's ' Systema 

 Naturae '^ where he quotes Chemnitz, and under the impression it 

 was a sinistral species calls it Nerita perversa. This, however, is 

 such a complete misnomer that it seems wiser to set it aside, as 

 recommended in such cases by the British Association Rules, and to 

 adopt the specific name of conoideus conferred on it by Lamarck\ The 

 generic name of Velates proposed by Montfort* should also be adopted, 

 since, judging from the evidence afforded by its shell, the animal 

 must have differed in important respects from both of its nearest 

 allies — Nerita and Neritina. Other conchologists have described 

 and figured the shell, notably Deshayes, who also first figured the 

 operculum ; but all save Schmidel ' seem to have confined their 

 attention to its external aspect and to have overlooked its internal 

 arrangement and its remarkable mode of growth after the earlier 

 stages of its existence have passed. Before, however, this can be 

 dealt with it is necessary, in the first instance, to briefly describe 

 certain features in the internal structure of other members of the 

 family to which it belongs. 



The Neritidse, it is well known, avail themselves largely of the 

 moUuscan faculty of removing portions of the shell that may be in 

 the way of the animal in the course of its growth, and some of them 

 in this manner convert the interior of their tenement into a single 

 open chamber across which there projects from the side, immediately 



1 Mart, and Chemn. Conch.-Cab. ix. (1786) p. 130. 



- Linnaeus, Syst. Nat., ed. cura Gmelin (1789), torn. i. p. 3G86. 



^ Nerita conoidea, Ann. Mus. Paris, v. (1804) p. 93. 



^ Conch. Syst. ii. (1810) pp. 354-fi, fig. 



' A list of the more important references is given at the end of this paper. 



