414 Dr. J. E. Gray on the Tongues of Mollusca. 



each other with certainty without the examination of the oper- 

 culum ; and Dr. Loven has shown that there are some genera, — 

 Buccinum and Trichotro-pis for example, which have the animal, 

 shell, and operculum so like each other, that the latter genus is 

 only to be known by a certain prolongation of the periostraca 

 on the keel of the last whorl, — which have the tongue so unlike, 

 that I believe they ought to be considered as the types of different 

 families ; and Dr. Troschel in his system would place them in 

 two distinct suborders, the genus Buccinum being referred to 

 Proboscidea, and Trichotropis to Tcunioglossa. 



Dr. Troschel gives a striking instance. Triton succinctum 

 has been considered as a typical species, having the usual ani- 

 mal and operculum of the genus, yet Dr. Troschel describes and 

 figures the tongue as having the seven series of teeth of his 

 TiBnioglossa. 



The similarity of appearance of the animal and shell of Ancil- 

 lari'a and Oliva are great, yet Dr. Loven has figured the teeth 

 of the former as very like those of Nassa and Buccinum, the ty- 

 pical genera of the Buccinida ; but Dr, Troschel has very lately 

 figured the teeth of Oliva peruviana, and they are so different, 

 that he thinks I have inaccurately referred these two genera to 

 that family, and proposes to form for them a separate family 

 (see Wiegmann^s Archiv, 1852, 166). 



The same similarity of the animal and shell exists between the 

 genera Cyprcea and Ovula, yet Dr. Loven and Troschel have de- 

 scribed and figured the teeth of different species of Cijprcea, show- 

 ing them to be nearly typical TcBnioglossata ; and the latter has 

 very lately figured the teeth of Ovula tuberculosa (Wiegmann^s 

 Archiv, 1852, 163. t. 7- f- 6), which are so unlike those of any 

 mollusc before known, that they must belong to a peculiar 

 family ; however, the specimen he examined was in such an im- 

 perfect condition, that he was not able to describe their position 

 on the tongue. Several other instances of the kind might be 

 cited. 



In the outline of the system of Gasteropodous Mollusca, ap- 

 pended to the explanation of the plates of Mrs. Gray's ' Figures of 

 Mollusca,' I have attempted to combine the labours of Dr. Loven 

 with my own observations on the animal and operculum, but 

 every day adds to our knowledge of these animals, and renders 

 constant revision necessary. 



Dr. Troschel in a late paper (Wiegmann's Archiv, 1852, 166) 

 observes on this essay : " Mr. Gray, in his systematic arrangement 

 of the Gasteropoda, has proceeded exactly upon my principles, 

 and being assisted by rich materials and a perfect knowledge of 

 bibliography has done much that is excellent, although in parti- 

 cular instances many errors have slipped into his work. He has. 



