Mr. W. H. Benson on Camptonyx. 889 



shelly tube which coininunicutes with the interior in so many of 

 the mountain-loving oriental Cyelostomidw. 



In Mr. Woodward's drawings, the position of the ocular 

 points, widely separate from each other, is on the upper side of 

 the head. They are sessile at the middle of the hinder part of 

 the base of the short obtuse tcntacula, and are visible only from 

 above; whereas in Gray's figure of Aiici/lus (no. 52. p. 216, ed. 

 noviss. Tiirton) the eyes appear below, and are stated to be placed 

 on a small lateral lobe on the side of the base of the triangular 

 truncated tentacle*. In Lymnaa, where the eyes appear on the 

 upper side of the head, they are in front, prominent, and ap- 

 proximate to each other. The position of the eyes in Pythia 

 (Scarahus), which I had an opportunity of examining some 

 twenty-three years ago at Calcutta, more nearly represents that 

 of the corresponding organs in Camptonyx. 



The littoral genus Siphonaria, which Dr. Gray places between 

 the Auriculida3 and Cyclostomidje, is remarkable for the presence 

 of a deep siphoual groove on the right side. Again, the large 

 Tertiary fossil genus Valenciennia, Rousseau, supposed to have 

 been an inhabitant of brackish water, has a channel running 

 from the under side of the beak of the shell to the right side of 

 the aperture, much like the dorsal one of Camptonyx. It is 

 supposed by M. Bourguiguat to serve as a sheath to a siphoual 

 tube. It probably communicates, as in Camptonyx, with the 

 respiratory orifice, and does not necessarily contain a special 

 organ. The strong concentric ribs of Valenciennia present a 

 curious analogy to the rugose surface of Camptonyx. 



l/th April, 1858. 



EXPLANATION OF PLATE XIL 



Fig. I . fl, Shell of young Camptonyx viewed from the ajjcrture ; b, dorsal 



view; c, side view. 

 Fig. 2. d. Adult shell ; aperture ; e, dorsal view. 

 Fig. '^. Live aaiuial in the shell ; /, siphon. 

 Fig. 4. Dead animal in the shell; g, muzzle. 

 Fig. 5. Dead animal extracted fi-om the shell, dorsal view. 

 Fig. 6. Ditto; h, respiratory orifice; i, adductor muscle. 

 Fig. 7. Teeth. 



All the figures are greatly magnified. 



* Dupuy's description of the animal of Aacylus, and the details given 

 in Moquiu-Tandon's ' MoUusques de France,' plates 35 & 3G, help to con- 

 firm the diflFerences observed. 



22* 



