BIVALVIA. 99 
6 PrcruncuLtus proximus, 8. Wood. Tab. XVI, fig. 5, a—e. 
Spec. Char. P. testa oblique suborbicularé, inequilaterali, crassd, tumidd ; obsolete 
costulata vel radiata ; siphoni-regione subangulato ; umbonibus prominulis ; ared connewiis 
obtusé triangulari ; dentibus numerosis. 
Diameter, 1+ inch. 
Locality. Barton (Edwards). 
This species differs from P. pulvinatus, with which it has been hitherto associated, in 
being more oblique, more elevated, and less tumid, and there is always a greater extension 
of the siphoni-lateral margin, with a depression or flattened space above a slight ridge, 
extending from the umbo on that side, particularly in elevated specimens. The shell in 
general has a greater diameter in the direction of its height, and in these specimens the 
ligamental area is larger or higher, with the dental margin broader than in others ; but its 
principal distinction is the angular ridge on the siphonal side. Tab. XVII, fig. 11, is 
from Huntingbridge, and may, I now think, be referred to this species; it was at first 
supposed to be a Zimopsis, but the character which induced that name is probably acci- 
dental ; it is, however, smoother and thinner than the generality of the Barton specimens. 
There are two or three species from the Paris basin to which our fossil bears a close 
relationship, but to no one of them can I satisfactorily assign it. P. depressus (Desh.) 
resembles it in outline, but our shell is neither depressed (‘‘depressissima’’), nor thin; it 
is crenulated all round, not ‘“ mince et lisse antérieurement et postérieurement ;” neither 
is the “area ligamenti minima.” 
7. Pecruncutus putvinatus, Lamarck. Tab. XVI, fig. 2, a, 6. 
PECTUNCULUS PULVINATUS. Lam. Ann. du Mus., t. vi, p. 216, and t. ix, pl. 18, fig. 
9, a, 6. 
— _ Desh. Par. Foss., p. 219, pl. 35, figs. 15—17. 
—_ _ Ib. Coq. Caract. des Terr., pl. 5, figs. 9, 10. 
— — Bronn. Leth. Geogn., t. li, p. 936, pl. 39, fig. 4. 
— — Goldf. Petr. Germ., p. 160, No. 5, pl. 126, fig. 5. 
— — Nyst. Belg. Foss., p. 250, pl. 19, fig. 8, a, 4. 
— — J. Sow. in Dixon’s Geol. of Suss., p. 93, t. 11, fig. 25. 
— — Bronn. Syst. der Urw., p. 52, pl. 5, fig. 13, 1824. 
Spec. Char. P. testé orbiculatd, ventricosd aut pulvinatd, subequilaterali viv obliquata. 
striato-costulatd vel radiata, tenué decussata ; margine crenato, crenulis brevibus ; ared car- 
dinali perangustd, umbonibus depressis. 
Shell orbicular or lenticular, ventricose or puffed up, nearly equilateral, slightly 
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