478 FISSURELLID.E. 



Berwick Club, vol. ii. p. 33. — Macgil. Moll. Aberd. p. 

 178.— Brit. Mar. Conch, p. 133 (not var.).— Brown, 

 lUust. Conch. G. B. p. 62, pi. 1-2, f. 17, 1.9.— Potiez and 

 Mich. Gal. Douai, Moll. p. 519, pi. 36, f. 15, 16. 

 Emay<ji7iula lavis, Recluz, Revue Zoolog. Cuvierienne, 1843, p. 232. 



„ curvirostris (young), Macgil. (not Dash.) Moll. Aberdeens. p. 331. 



The collection of Linnaeus having confirmed the decision 

 arrived at by M. Recluz solely from a critical perusal of the 

 " Systema Natures, " that this is not the Patella fissur a of 

 the author of that work, we are compelled to find another 

 name for this well-known shell. The specific epithet Ixms 

 must be rejected, since, besides its incorrectness, it was 

 applied through an erroneous impression that this was the 

 Patella l^vis of Pennant. 



When adult this shell is conical, strong, and opaque, 

 with the vertex simply and slightly recurved, and not even 

 hooked : when young the texture is thin and semitrans- 

 parent, the shape much more depressed, and the vertex 

 acute, much curved, and almost obliquely subspiral; in 

 all stages, however, a line let fall from the vertex would 

 fall within the margin. The shell, which exhibits a slight 

 lateral compression, the side surfaces being but little con- 

 vex, is both within and without of a more or less clear 

 white ; the front dorsal outline is only moderately arched. 

 The base, which is oval or elliptical, is rounded, and of 

 nearly equal breadth at both extremities, and slightly or 

 else moderately convex at the sides, but usually bulges out 

 a little at the hinder part of the left one. The marginal slit, 

 which is long, very narrow, slightly oblique, and as broad 

 above as below, reaches to about two-fifths of the direct 

 (not the superficial) height, but rather exceeds that propor- 

 tion in the young, rather falls below it in the adult. Its 

 previous course is indicated externally by a simple sulcus, 

 that merely exhibits fine and closely set concentric sti'ise. 



