BIVALVIA. 163 
1. CrassaTELLA Bartonensis, Ldwards MS. PI. XXIV, fig. 7 a, 6. 
Spec. Char. Cr. Testé orbiculato-trigonuld, crassiusculd, subaquilaterali, compressa ; 
regulariter sulcaté vel lamellaté; lamellis distantibus, simplicibus ; umbonibus acutis 
elevatis ; pedi-regione vir minore ; ani regione superné declivi; lunuld minima, depressd, 
levigaté ; cardine brevi; in valvd dextraé unidentato, valud sinistra bidentato ; dentibus 
lateralibus elongatis ; marginibus integris. 
Shell roundedly trigonular, not very thick, nearly equilateral, compressed, externally 
sulcated or laminated ; ridges distant, rounded and depressed ; beaks sharp and prominent ; 
pedal region a trifle the smaller of the two; dorsal margin sloping; lunule small, 
depressed, elongated; hinge short, denticles sharp; lateral teeth narrow, elongated ; 
margin smooth. 
Diameter, 2ths of an inch. 
Locality. Barton (Ldwards). 
‘Two specimens of this species are all that I have seen, and they are both from the 
same locality. The principal distinction is the exterior ornament, the ridges or lamella 
being more distant than on any other of the suborbicular species of this genus. These 
ridges are very regular and cover the entire surface. The diagonal ridge on the siphonal 
or anal side, so conspicuous on the transverse species, is scarcely perceptible. 
2. CrassateLLA Bronnit(?), Merian. Pl. XXIV, fig. 2 a—c. 
CRASSATELLA Bronnit, Merian. In Litteris Sandb., 1853, sec. Deshayes. 
—_— Desh, An. sans Vert. du Bass. de Par., vol. i, pl. xix, figs. 12—14, 
and pl. xx, figs. 22—24, 1860. 
Spec. Char. Cr. Testdé minima, ovato-trigond, inequilaterali, transversim sulcata ; 
umbonibus minimis, acutis, proeminentibus ; latere antico breviore ; postico subtruncato , 
lunuld minima, depressd, levigatd, ovato-lanceolata ; cardine brevi, bidentato, alterd uniden- 
tato, dentibus angustis, elongatis ; marginibus integris. 
Shell small, roundedly trigonal, slightly inequilateral, covered with regular and rather 
close-set concentric ridges; beaks small and somewhat prominent, sides unequally 
rounded ; lunule small, smooth and ovately elongate; hinge narrow, one tooth in the 
right valve and two in the other; margins smooth. : 
Diameter, $ an inch. 
Localities. Highcliff, Barton, Stubbington (Zdwards). 
France; Jeures, Etrechy (Deshayes). 
