306 Zoological Society :-— 



2 feet 2 inches, and of the female 2 feet. The height of the largest 

 or male hird, when erect, to the top of the head, was 3 feet 2 inches, 

 and of the female 3 feet. 



Description of the Adult State of Voluta mamilla, 

 Gray. By Dr. J. E. Gray, F.R.S., V.P.Z.S., etc. 



We have had in the British Museum for years a young specimen 

 of a shell from Van Diemen's Land, which I named Voluta ma- 

 milla. It is figured under that name in Sowerby's ' Conchological 

 Thesaurus,' t, 50. f. 57, 58 ; it is described by me in my "Obser- 

 vations on the Species of Volutes," Proc. Zool. Soc. 1855, p. 55, 

 under the name of Scapha mamilla ; and it is noticed under the genus 

 Cymhium by the Messrs. A. and H. Adams, in their * Genera of 

 Mollusca.' 



But many conchologists have been incHned to regard this specimen 

 as a mere monstrosity of some other species, — an idea that could only 

 have been entertained by such as were ignorant of the general struc- 

 ture and physiology of molluscous animals. 



We have lately received from Van Diemen's Land three fine spe- 

 cimens of this shell, — two of them fully grown, and the other inter- 

 mediate in size between the young specimen we formerly possessed 

 and the adult state of the species. It may be observed that these 

 shells were all taken while the animals were growing ; the shells have 

 consequently the thin edge incident to that state of the animal, and 

 not the rounded thickened edge to the outer lip which the shell as- 

 sumes while it is in a state of rest after its former growths. Though 

 probably the full size of the species, they are none of them what 

 conchologists generally call adult shells. But this form of the outer 

 lip is no proof of the adult state of the shell ; for the animal con- 

 stantly increases the size of the shell after such thickening and 

 periods of rest ; thus the thickening of the edge of the lip is only 

 a proof that the shell was taken and the animal destroyed while the 

 animal and shell were not increasing their size. 



The adult shell greatly resembles Scapha magnifica in form and 

 colouring ; but the apex is much larger, irregular, with the apex of 

 the whorl on one side of the tip ; and the system of colouring is much 

 broader, and coarser in its character. 



ScAPHA MAMILLA. 



Shell ovate; nucleus very large, spire rather irregular, one- 

 coloured, orange, with the apex on one side ; the last whorl irregu- 

 larly markled with dark purple-brown lines having triangular pale 

 spots, and with a subcentral and broad posterior sutural colourless 

 band. Pillar dark orange, with three oblique plaits. Throat 

 yellow. 



This form of the nucleus is found in another species of the genus 

 Scapha^ but not in such a highly developed state, viz. in Scapha 

 fusiformis, also inhabiting Van Diemen's Land ; and it is also found 

 in the genus Fulgoraria. 



