CUITON. 413 



rufous brown (the smaller the specimen the more vivid, 

 for the most part, is the tint), either uniform, or va- 

 riegated with a marbling of white or green on a ground 

 which is more dusky in the large northern examples, 

 than in the smaller but more elegant southern ones. The 

 surface of the plates, which are comparatively long con- 

 sidering their narrowness, is a little shining, and to the 

 eye apparently smooth ; a powerful lens reveals an ex- 

 tremely minute depressed kind of obscure and irregular 

 shagreening. The division of areas is only, if at all, 

 indicated by the sudden elevation of surface at the com- 

 mencement of the lateral triangles ; the concentric lines 

 of growth are not unfrequently a little prominent. The 

 declivity at the termination of the posterior mucro is 

 not abrupt. The connecting or ligamental border is re- 

 markably broad, that on each side of the fifth plate oc- 

 cupying together from two-sevenths to (in the young chiefly) 

 even two-fifths of the entire width. It is a little glossy, 

 very closely reticulated in diamonds, and if not display- 

 ing the mottled painting of the testaceous plates, is often 

 curiously marked on its red ground with two pair of 

 conspicuous white spots, situated in a line with the sutures 

 of the terminal plates at either extremity. 



Mr. Lowe observes that there are twenty small inser- 

 tional teeth on the first plate, and four, of which the 

 first is larger than the rest, upon each side of the middle 

 valves. He remarks, likewise, that the C. septemvalvis of 

 Montagu (Test. Brit. p. 3. — C. discors, Maton and Rack. 

 Trans. Linn. Soc. vol. viii. p. 20. — Brown, 111. Conch. G. 

 B. p. 67) belongs to the present species rather than to the 

 marginatum of authors, its margin being described as 

 reticulated. One of our larger examples measures half 

 an inch in breadth, and fully eleven lines in length. 



