162 MOLLTJSCA FROM THE CRAG. 



the vertex is generally 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 maybe 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 distin- 

 guished. The specimen sent by Mr. Thompson was dredged in deep water off 

 Cape Clear by Mr. M 'Andrew. 



3. Tectuea (?) paevula. Woodward. Tab. XVIII, fig. 8, a — b. 

 Lottia parvula. S. Wood. Catalogue 1842. 

 Patella parvula. Woodward. Geol. of Norf. t. 3, fig. 1, 1833. 



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

 tenuissime striatic ; 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, ^ ; 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 strias, and the margin is 

 crenulated. This may possibly be the young of an elongated variety of Patella vulgata. 



Scissueella,* VOrbigny, 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, conse- 



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



