160 LITTORINIDiE. 



at both ends — characters which assuredly remove it from 

 the family to which SJceiiea belongs, and place it where 

 Philippi indicates. But until the animal of onr British 

 shell be examined, we hesitate to assign it such a po- 

 sition. 



It appears to have a wide range. Guernsey, Arran 

 (Barlee) ; Donegal in Ireland (Warren) ; and Zetland. 



S.? ROTA, Forbes and Hanley. 



Extremely minute, with ribs radiating from the sutures. 



Plate LXXIII. fig. 10; Plate LXXXVIII. f. 1, 2. 



A miniature Ammonite conveys the best idea of this 

 beautiful but most minute shell. It is discoid, flattened 

 on both sides, but scarcely sunken in the middle, and 

 of a somewhat pearly semi-transparent white, or very 

 pale wax-colour. Both the upper aud lower disks are 

 adorned by numerous abruptly projecting rounded ribs, 

 that dilate as they radiate from the well-marked su- 

 tural line, but do not quite extend to the edge of the 

 volutions, and are separated by intervals of nearly equal 

 size, that are either smooth or else present a single 

 elevated radiating line ; just before the termination of the 

 ribs an obscure spiral groove occasionally runs between 

 them, but does not traverse the ribs themselves. There 

 are only two whorls and a half, that are convex, well- 

 defined, and slowly enlarge from a smooth and tolerably 

 large apex. The body is not regularly rounded, but 

 seems, possibly from the lesser convexity of the periphery, 

 a little subangulated botli above and below. The aperture, 

 which is raised above the level of the upper disk, is small, 

 and nearly circular, as the penult whorl projects but 



