GIBBONS : ON OMALONYX UNGUIS AND O, FELINA. 99 



COMPARISON OF OMALONYX UNGUIS, D'Orb., 

 WITH O. FELINA, Guppy. 



By J. S. GIBBONS, M.B. 



Last year I discovered in Demerara an Omalonyx that was 

 pronounced by Mr. Guppy to be identical with the Trinidad 

 species O.felina. I have since collected the O. unguis of D'Orb. 

 at Bahia, and I find (contrary to my expectations) that there is a 

 decided difference between the two, but of a comparative nature 

 only. 



The soft parts of O. unguis are as follows: — Body, when 

 moderately extended, cylindrico-lanceolate, high and truncate in 

 front, broad opposite the shell, and tumid, sloped and tapering 

 towards posterior end, which is somewhat acutely pointed ; mar- 

 gins of foot opposite the shell a little expanded; the surface is 

 irregularly and sparingly granulate, lubricated, shining; mantle 

 thickish, prolonged a little over dorsum, and investing edge of 

 shell for a short distance; tentacles, upper pair conical, shortish, 

 thick and somewhat triangular at the base, where they arise close 

 together, bulbs blunt and rather thick; lower tentacles cylindrical, 

 very short and thick; color of animal opaque, greyish-white, often 

 with a yellowish tinge, speckled with faint cinereous grey spots, 

 sometimes few, occasionally nearly absent; a couple of broad 

 longitudinal streaks of dark purplish brown pass from each end 

 of the shell to the anterior and posterior extremities of the animal 

 (in the latter case converging to the lip, in front passing to the 

 base of the upper tentacles, and thence up to the bulbs); the 

 shell is situated in the middle of the dorsum, the spire directed 

 backwards; under the spire and easily seen through the transparent 

 shell, there is a dark brown patch from which three or four streaks 

 of the same color radiate to the anterior margins of the shell. 



Length about i| in., by | in. in breadth. 



