116 Dr. J. E. Gray on the genera Camptonyx and Tanysiphon. 



XIII. — Observations on the Genera Camptonyx and Tanysiphon 

 of Benson. By Dr. J. E. Gray, F.R.S., V.P.Z.S. &c. 



In a preceding Number of the ' Annals'* I have pointed out the 

 affinity of the genus Camptonyx to Otina, simply from the de- 

 scription of the animal ; but, now I have had the opportunity of 

 seeing the figures, I am convinced of the soundness of the com- 

 parison, and indeed I am almost induced to believe that Cam- 

 ptonyx is only a very slight modification or subsection of that 

 genus, as the lateral groove is much slighter than I had expected, 

 and the shell is an Otina as well as the animal. 



I may further add, that the South American genus Chilina, 

 which has been referred to Auriculadce and Lymneadce, if the 

 figures and description of the animal by D'Orbigny and Dr. 

 Gould are correct, is evidently another genus of the same family. 



The figure of the teeth of Camptonyx does not justify the 

 assertion of their similarity to those of Ancylus, as may be 

 proved by comparing the figure in the ' Annals' with those of 

 Ancylus given by Dr. Otto Goldfuss and others, or the description 

 of the teeth of Ancylus and Velletia given by Mr. W. Thomson 

 in the ' Annals/ 



All that can be said is, that they have the normal teeth of the 

 Pulmonata, with certain generic or specific peculiarities. 



In the same Number of the f Annals/ Mr. Benson described 

 an interesting genus of freshwater bivalve mollusk found living 

 in the slaty clay banks of the River Jumna. 



I cannot understand how any conchologist could have doubted 

 its distinctness from Novaculina, either malacologically or con- 

 chologically. It appears to me equally extraordinary how a 

 shell with external cartilage and diverging cardinal teeth can be 

 placed in Myacidce, unless the latter family is to have a much 

 more extended sense than I am willing to give to it. It appears 

 to agree with Mya, as far as I can discover by the description, 

 only in two particulars, for the number and extension or non- 

 extension of the gills in the siphon are not noticed : — 



First, that the siphons are united; and secondly, that the 

 apex of the siphons near the aperture is surrounded with a 

 ring of tentacles, and the aperture of the branchial siphon is 

 bearded. The union and non-union, and the extent of the union 

 of the siphons, have been proved, by the examination of a number 

 of animals, not to be of much importance, certainly not afford- 

 ing a family character : indeed, very nearly allied genera of the 

 same family frequently vary in these particulars ; several genera 

 besides Mya, with united siphons, have a ring of tentacles 

 round the base of the two apertures. 



* Ann. Nat. Hist. 3 ser. vol. i. p. 406. 



