162 MOLLUSCA FROM THE CRAG. 



vertex is o-enerally eroded ; when perfect, it is rather acute. The rays are regular in 

 distance upon the same specimen, though very variable in number. A recent specimen, 

 obligingly sent to me by William Thompson, Esq., for comparison, is perfectly ovate in 

 the base, with more numerous rays than in the generality of my specimens, which 

 are however, rather variable in that character ; when perfect, the tuberculated rays 

 will distinguish it, and may be considered a fair identification. 



Some small specimens from the Red Crag, which had been considered as the young 

 of T. virginea, may possibly belong to this species, as they are the same in form, but, 

 having lost the tubercles or granules from the rays, cannot be distinguished. The 

 specimen sent by Mr. Thompson was dredged in deep water off Cape Clear by 

 Mr. M f Andrew. 



3. TECTURA (?) PARVULA. Woodward. Tab. XVIII, fig. 8, a b. 

 LOTTIA PARVULA. S. Wood. Catalogue 1842. 

 PATELLA PAKVULA. Woodward. Geol. of Norf. t. 3, fig. 1, 1833. 



T. Testa oUongo-ovatd, elongatd, costatd vel radiatd ; inter stitiis, longitudinaliter 

 tenuissime striatis ; vertice obtuso, eccentrico. 



Shell oblong-ovate, elongate, costated, or rather radiated, very finely striated 

 between the rays, with an obtuse vertex before the centre of the shell. 



Length, I ; breadth, of an inch. 



Locality. Mam. Crag, Bramerton. 



This shell appears to be rare. My cabinet contains but one specimen, which, with 

 two others belonging to Mr. Wigham, are all I have seen ; it agrees with Woodward's 

 figure, but I am not acquainted with any recent form that it precisely resembles ; it 

 differs from either of the other species in the fewer number and subangular form of 

 its rays as well as in the more oblong form of its base. Between the rays the shell is 

 covered with very fine longitudinal striae, and the margin is crenulated. This may 

 possibly be the young of an elongated variety of Patella vulgata. 



SCISSURELLA,* D' Orbigny, 1823. 



Gen. Char. Shell small, thin, and fragile, subglobose, with, generally, a depressed 

 spire ; aperture subcircular or ovate, modified by the elevation or depression of the 

 spire ; peritreme sharp, with a deep sinus or slit, sometimes an oblong foramen in the 

 outer lip, with a sort of double keel on the outside formed by the reflected edge of the 

 sinus ; base of the shell with a generally large, open, and deep umbilicus. 



The animal of this genus is at present unknown, and its position is, consequently, 



* Etym. Scissus, cut, divided, a scindo. 



