DISCINA. 159 
really the same. In that case Ch. Phillipsii would become a synonym of 
Oh. convolutus; but it is certainly distinct from Ch. Hardrensis, with which 
Ch. convolutus was formerly united by Davidson. Under the circumstances it 
seems best to retain the name for the present upon the Lummaton list. 
2. Orper.—INARTICULATA, Deshayes, 1836. 
I. Family.—Discinipa, Gray, 1848. 
1. Genus.—Discina, Lamark, 1819. 
1, Disorna peLtTastes, n. sp. Pl. XVII, fig. 14. 
Description.—Ventral or pedicle valve rather large, slightly conical, elongate 
oval, apparently rather steeper and narrower behind. Apex posteriorly sub-central. 
Sulcus unknown. Internal pedicle-area apparently minute and elongate, with the 
lateral callosities coalesced to form a small tube with a minute foramen, only 
produced a little in front of the centre of the shell. Surface ornamented with 
numerous very fine and rather irregular concentric threads, separated by wider 
interspaces. Shell-structure very thin. 
Size.—Length, 22 mm.; width, 16 mm. 
Locality.—A single specimen is in my Collection from Lummaton. 
Remarks.—This shell is widely different from the Orbiculoidea (Discina) nitida, 
Phillips,’ described from North Devon. It seems characterised by its compara- 
tively large size, its elongate form, and its numerous fine concentric lineations. 
The only specimen I know is rather obscure, being defective and obliquely com- 
pressed. It lies in the matrix with the inner surface exposed, but the character of 
the surface-ornament is sufficiently apparent, except where covered by callosities. 
Rather below the centre is a minute tube, which seems to me to be undoubtedly 
the internal opening of the pedicle-groove. This appears to be accidentally 
fractured above, the actual foramen opening downwards. If this is so, the arrange- 
ment seems to indicate that it belongs to the genus Discina as restricted by Dall” 
and Hall* to the recent group of Discina striata, Schumacker, sp.* (not Sowerby), 
rather than to Orbiculoidea, &c., to which Hall refers the Paleozoic Discine gener- 
1 1865, Davidson, ‘ Brit. Foss. Brach.,’ vol. iii, pt. 6, p. 104, pl. xx, figs. 9, 10. 
2 1871, Dall, ‘ Bull. Mus. Comp. Zool. Harvard College,’ vol. iii, pt. 1, p. 39. 
3 1892, Hall, ‘ Pal. N. Y..,’ vol. viii, pt. 1, p. 122, pl. iv x, figs. 23, 24. 
* 1817, Schumacher, ‘ Essai Nouv. Syst. Vers Test.,’ p. 102, pl. xx, figs. 1 a—f. 
