124 Dr. J. E. Gray on the Division of Ctenobranchous 



XIII, — On the Division of Ctenobranchous Gasteropodous Mol- 

 lusca into lai-ger Groups and Families. By J. E. Gray, Ph.D., 

 F.R.S., V.P.Z.S. &c. 



CuviER, Dumeril, and Lamarck separated the Gasteropodous 

 Mollusca, which have pectinated or comb-like gills, into two di- 

 visions, according as they possessed or were without a siphon 

 to facilitate the admission of water to their gills, probably being 

 influenced by preceding conchologists, who had in a similar 

 manner divided the spiral shells into those which had an entire, 

 or an emarginated, or a channelled mouth. Lamarck called 

 those with a siphon Zoophaga, and those without it Phyto- 

 phaga, believing the food of the molluscs to be indicated by 

 the form of the mantle. As we have become moi'e acquainted 

 with the habits of the Mollusca, it has been observed that 

 many of the animals without any siphon to the mantle, as 

 Natica, Scalaria, lanthina, &c., are quite as carnivorous as those 

 which have the siphon most perfectly developed ; on the other 

 hand, Lamarck found it requisite to arrange many genera, as 

 Cerithium, Melanopsis, Planaxis, &c., with the Phytophaga with 

 entire mouths, though the animals have as well-developed siphons 

 and the shells as distinct canal or siphonal notch, as any of the 

 genera of Zoophagous Mollusca. These divisions, however, have 

 been almost universally adopted. Dr. Loven in his paper on 

 the Scandinavian Mollusca and on the Tongues of these animals, 

 divided the Gasteropoda into natural families independent of 

 these divisions, and Dr. Troschel in his arrangement of Mol- 

 lusca has followed the same course, separating the families 

 into groups according to the structure of their tongues. The 

 observations which Dr. Troschel made on the arrangement which 

 I published in Mrs. Gray's work, * Figures of Molluscous 

 Animals,' have induced me to reconsider the subject, consult 

 again all the authorities, and examine the tongues of the mol- 

 luscous animals which have been lately received at the Museum 

 collections. 



Being impressed with the importance which Dr. Loven at- 

 tached to the form of the mouth, I was induced to pay attention 

 to this character, and I believe that it affords a much more na- 

 tural one to separate families into two great groups, than the 

 presence or the absence of the siphon of the mantle, and one 

 which appears to be more consistent with the habits of the animal 

 and much less liable to exceptions. I may observe in passing 

 that some of the French zoologists do not appear to have been 

 impressed with its importance, for MM. Quoy and Gaimard in 

 some few instances erroneously represent some of the species of 

 a geiuis, as a Murex and Terebra, for example, as having a 



