21 
THETIS minor. 
TAB. DXIXL —Jigs. 5 and 6. 
Spec. Char. Gibbose, wider than long ; posterior 
edge rounded. 
Syn. Venus. Mantell,GeoL of Sussex, p. 73. no. 12. 
Generally about an inch wide, but sometimes nearly 
an inch and a half : it is more convex and has larger beaks 
than the preceding species ; the surface has the same 
kind of punctums, but they are very seldom to be traced 
in the circumstances under which the individuals are 
commonly presented to us. 
An immense number of very perfect casts of this neat 
shell occur in the hard ferruginous masses of the lower 
Green-sand at Parham Park in Sussex, and Shanklin 
Chine in the Isle of Wight. Specimens from the former 
spot have long been in Mr. Sowerby’s Museum, where 
they were deposited by G. Mantell, Esq. ; those from the 
latter place (fig. 6.) were collected by my father himself, 
in 1818. H.T. DelaBeche Esq. has also discovered it in the 
lowest Green-sand near Lyme Regis, where the earthy 
matter of the shell still remains (fig. 5.) ; but the shells 
