HOMALOGYRA. 71 



Spawn-capsules which are occasionally found in the up- 

 per cavity of the last whorl in dried specimens, and which 

 may be presumed to belong to the Homalogyra, are of a 

 tawny colour and oval, with a wide slit or orifice at the 

 top of each, and agglutinated together in a cluster of 

 5 or 6 ; they are much larger than the capsules that I 

 have observed of any Rissoa. 



Philippi must have made a mistake (an infirmity that 

 is common to us all) in describing and figuring this 

 moUusk as similar to the animal of Truncatella trunca- 

 tula ; and in the same work ( Archiv fiir Naturgeschichte, 

 vii. pt. i. p. 53, t. V. f. 7) Assimmea litorina is equally 

 misrepresented. Instead of all these three species 

 having the eyes seated on the inner base of the tentacles, 

 one only [T. truncatula) can be said to be in this cate- 

 gory. H. atomus has not the slightest appearance of 

 tentacles ; and in A. litorina the eyes are placed on their 

 tips. 



The present species was regarded by the authors of 

 the ' British Mollusca ' as Adamses Helix nitidissima. 

 But that shell is evidently the fry of Zonites radiatulus, 

 his H. bicolor being the fry of Z. cellarius. L. PfeifFer 

 referred our shell, with a doubt, to his genus Paludinella. 

 It is the Ammonicerina simplex of Costa. 



2. H. ROTA"^, Forbes and Hanley. 



Skenea rota, F. & H. iii. p. IGO, pi. Ixxiii. f. 10, and Ixxxviii. f. 1, 2. 



Shell resembling in shape a miniature Ammonite (of the 

 section Capricorm, De Buch), thin, semitransparent, and lus- 

 trous : sculpture, several ring-like ribs, from 20 to 25 on the 

 last whorl of a full-grown specimen, besides 3 spiral keels 

 (which vary in strength and are not always perceptible) and 

 a few fine intermediate striae ; one of these keels encircles the 

 periphery, and the other two the middle of each whorl on the 



* A wheel. 



