52 MOLLUSCA FROM THE GREAT OOLITE. 



Testa parvd, Iteviusculd, ovatd, convexd, obliqud, umbonibus anticis, latere antico 

 brevissimo, latere postico, oblique declivi, basi ellipticd curvatd, lineis concentricis irregu- 

 laribus tenuissimis. 



Shell small, smooth, ovate, convex, oblique, umbones anterior, anterior side very short, 

 posterior side lengthened, its border obliquely sloping, base curved elliptically, lines con- 

 centric, irregular, and very fine. 



This small shell is common throughout the shelly beds of the Minchinhampton district, 

 where its figure is much less variable than in the specimens from Ancliff, which are figured 

 in the ' Mineral Conchology,' so that it is not easily mistaken for any other contempo- 

 raneous species. 



Localities. Ancliff and Minchinhampton. 



NTJCULA WALTONI, Tab. V, fig. 14. 



Testa parvd ovatd subcompressd, umbonibus acuminatis, anticis, latere antico rotunda, 

 postico elongato et subrostrato. 



Shell small, ovate, rather compressed, umbones acute and anterior ; anterior side short 

 and rounded, posterior side elongated and somewhat rostrated. 



The figure has some resemblance to N. acuminata, but the anterior side is much more 

 produced, the posterior extremity more pointed; there is a kind of obtuse ridge, extending 

 posteriorly from the umbo to the inferior and posterior extremity, and the junctions of the 

 valves posteriorly are compressed, and the surface is very smooth. It is very common in 

 the Clays of the Fullers-earth and likewise in the Bradford Clay, having the valves in 

 apposition ; in the shelly beds of the Great Oolite it occurs very rarely, and the valves 

 are disunited. 



Localities. The Cotswold Hills, at various localities in the Fullers-earth; the 

 Tetbury Road Railway Station, in the Bradford Clay ; Minchinhampton Common, in the 

 Great Oolite. 



This species is dedicated to that indefatigable collector, Mr. Walton of Bath. 



LEDA, Schumacher, 1817. 



NUCULA (pars), Lam. 

 LEMBULUS, Risso, 1826. 

 DACKOMYA. Agass., 1840. 



Gen. Char. Shell inequilateral, umbones small, contiguous, anterior side convex, its 

 margin rounded ; posterior side attenuated, posterior slope lengthened, and excavated ; 

 teeth numerous parallel, separated in the middle by a fossa, structure of the test fibro- 

 lamellar. 



