152 
CONCHIFERA. 
Dl ANCHORA. 
Somewhat gibbose, obliquely sub-ovate ; anterior side a 
little flattened below the beaks, ears unequal, beaks produced ; 
surface smooth, with numerous fino divergent ribs, and a few 
concentric distinct lines of growth. 
The Kelloways Rock, Kelloways. 
13. Plagiostoma pectinoides. —The Pectinated Plagios¬ 
toma, pi. LXVI. fig. 9. 
P. pectinoides. Sowerby, II. p. 28, pi. 114*, fig. 2. 
Oblong-ovate, considerably oblique, compressed, back some¬ 
what angular; beaks acute ; hinge-lino long, ears nearly equal, 
and rather largo ; both sides a littlo straight, the anterior one 
considerably exceeding the posterior; surfaco with twenty or 
more carinated, slightly divergent ribs, and the intervening 
furrows transversely striated; margin scolloped ; inside, plane. 
The Lias, Pickeridge, Yorkshire. 
14*. Plagiostoma cardiiforme. —The Cardium-shaped 
Plagiostoma, pi. LXVI. fig. 14. 
P. cardiiformes. Sowerby, II. p. 20, pi. 113, fig. 3. 
Nearly circular, inflated ; anterior side short and straight ; 
ears equal; beaks prominent; surface smooth, with numerous 
longitudinal divergent furrows, crossed by nearly obsolete 
trausverso stria', which aro hardly visible but in tho furrows, 
whero they have the appearance of minute punctures. 
Tho Oxford Clay, Cambridge, Kelloways Rock, Glouces¬ 
tershire, and the Inferior Oolite, Cotswold. 
15. Plagiostoma Brightonense. —The Brighton Plagios¬ 
toma, pi. LXI.** fig. 20. 
P. Brightonenscs. Mantell, Geo. Sussex, p. 204, pi. 25, 
fig. 15. 
Obovate, compressed, posterior side with an ear; anterior 
side concave, lunulatc, small and acuminated; surface with 
numerous divergent rounded ribs ; the margin cronulated. 
The Upper Chalk, Brighton. 
1G. Plagiostoma asperum. —Tho Rough Plagiostoma, 
pi. LXI* fig. 11. 
P. aspera. Mantell, p. 129, pi. 20, fig. 18. 
Obovate, sub-compressed, with numerous flat ribs, the edges 
of which are fringed with minute sharp prickles; lines of 
growth few. 
The Gray Chalk Marl, Hamsey, Sussex. 
17. Plagiostoma interstinctum. —The Divided Plagios¬ 
toma, pi. LXVI. fig. 11. 
P. interstinctum . Phillips, Geo. York, I. pi. 7, fig. 14. 
Obliquely obovate, sides straight about half way below the 
hinge ; beaks produced ; ears indistiuct; surfaco w r ith many 
sharp, somewhat irregular divergent ribs; margin crcnated. 
The Great Oolite, Whit well, Yorkshire. 
18. Plagiostoma rigidulum. —The Rigid Plagiostoma, 
pi. LXVI. fig. 7. 
P. rigidulum. Phillips, Geo. York, pi. 7, fig. 13. 
Elongated, sub-triangular, considerably obliquo; anterior 
side elongated and concave ; posterior side short and rounded ; 
ears unequal; that of the posterior side very small, anterior 
one extending a considerable way down tho side ; beak largo 
and obtuse; surface smooth, with many obliquo divergent 
rounded ribs. 
The Cornbrash, Scarborough. 
19. Plagiostoma obliquatum. —The Oblique Plagiostoma. 
P. obli(juatum . Sowerby, Geo. Tr. 2d Ser. II. p. 319. 
Tho Portland Stone, Thame and Brora. 
20. Plagiostoma IIermani ? — Hermans Plagiostoma, 
pi. LXVI. fig. 12. 
Plagiostoma IIermani. Phillips, Geo. York, I. pi. 14, fig. 18. 
Sub-rotund, slightly oblique ; anterior side straight, and a 
littlo concave below the beaks ; posterior side shorter than the 
other ; ears unequal, of medium size ; beaks slightly produced, 
surface smooth, with about 15 very flat longitudinal ribs, and 
a few’ remote lines of growth. 
In the Marlestone and Calcareous Nodules, Upper Lias, 
Yorkshire. 
21. Plagiostoma ambiguum. —Tho Ambiguous Plagios¬ 
toma, pi. LXVI. fig. 8 % 
Plagiostoma . Phillips, Geo. York, pi. G, fig. 23. 
Sub-triangular, sides nearly equal, hinge-line short, slightly 
oblique; beaks acute and produced; surface with about twenty- 
throo rounded divergent ribs, crossed by a few distant lines of 
growth; margins scolloped. 
Tho Mountain Limestone, Yorkshire. 
22. Plagiostoma Mantelli(?) —Mantell's Plagiostoma, pi. 
LXI.* fig. 41. 
P. Mantellx . Goldfuss, II. pi. 104, fig. 9. 
Obliquely semicircular; right side truncated; surface with 
radiating striae, and a few concentric ones, which become ob¬ 
solete on tho back ; the lunulo hollow and liueated. 
Tho Upper Greensand, Lvmo Regis. 
23. Plagiostoma dubium. —The Doubtful Plagiostoma, 
pi. LXVI. fig. 1G. 
Plagiostoma (?) Phillips, Geo. York, I. pi. V. 10. 
Obliquely ovate, anterior side nearly straight; posterior 
sido rouuded ; beaks obtuse; sui’faco with numerous flat, diver¬ 
gent ribs, which aro ohsoloto towards tho apex ; with a few 
remote lines of growth. 
The Oxford Clay, Yorkshire. 
Genus XXL—DIANCHORA. — Sowerby. 
Shell inequivalve,sub-triangular, obliquo, adherent; attach¬ 
ed valve provided with an angular hiatus instead of an umbo ; 
tho other valve auriculated, and with an obtuse umbo ; hinge 
destitute of teeth. 
1. Dianciiora striata. —Tho Striated Dianchora, pi. 
LXVI * figs. 1, 2. 
D. striata. Sowerby, I. p. 183, pi. 80, fig. 1. 
Triangularly-ovate, oblique, length and breadth nearly equal ; 
beak prominent; free valve obscurely ribbed ; ears small, and 
continuous along the sides of tho valves. 
Greensand, near Warmiuster, Dane's Dyke, Wiltshire and 
Blackdown. 
2. DiANcnoRA lata. —The Broad Dianchora, pi. LXVI.*, 
fig. 3. 
D . lata. Sowerby, I. p. 184, pi. 80, fig. 2. 
The attached convexity moderate; semicircular; beak of 
valvo produced ; free valve plain ; surface with obscure lines 
of growth, and provided with a few obsolete stria); edge very 
sharp. 
Chalk, near Lewes, Sussex. 
