254 Mr. Gray on Mdania Setosa. 



serves, after some fanciful conjectures respecting the use of these 

 bristles, that they are, " a formation altogether unprecedented 

 amongst this class of animals," and he appears to conceive that 

 these bristles are " rooted as it were into the body of the shell;' 

 and he is not certain whether there are two, or one, forked ia 

 each tubular spine. 



Now it happens that there are two specimens of this " new and 

 most extraordinary" Shell in the British Museum, one of which 

 was in the Cracherode Collection, n. 472, and named by Humphreys 

 *' Spirilla spinosa, fresh water spiral spincd shell, from Admiralty 

 Island, New Guinea," and another presented by Dr. Leach; both 

 have to my knowledge been exposed to public view for upwards of 

 three years, and I am very much inclined to believe that the Buc- 

 cinum aculeatitnioi Lister's Mantissa, t. 1055. f. 8. is intended for 

 this shell ; but from the name of Humphreys, 1 some time ago 

 named the specimen in the Museum Melania spincsa. 



On examining these shells, which only differ from the Melania 

 amarula in the sinus of the hinder (or upper of Mr. S.) part of the 

 outer lip instead of being left an open vaulted spine as in that 

 species, in this shell is closed into a tubular one with the Perios- 

 traca drawn in and inclosed in the tube, the processes of which 

 form these bristles; Mr. S. remarks, that " in the genus Valuta we 

 have many instances of shells being crowned with thin vaulted 

 spines ; but no examples can be produced of such coronated spines 

 being tubular or completely closed on their circumference, and 

 pervious at their summits :" this is all very true with regard io 

 Valuta^ but is that the only genus in which we are to look for an 

 analagous structure? If the common Neritina corona be examined, 

 which is a much more analagous shell, the spines will be found to 

 be tubular, and longer than in this Melania ; nor are the tubular 

 spines confined to fresh-water species, for they are common to 

 Murextubifer^ M. Triplex, and several other Murices; and to the 

 Vinnw and Pectines in bivalve shells. 



In the figures of this Shell, (PL VIII. /. 6, 7, 8.) the manner in 

 which the periostraca is gradually condensed on the side of the 

 sinus, and produced into the spine, is attempted to be illustrated; 

 the bristles are generally distinct from one another, but are some- 



