226 
THE GEOLOGIST, 
Discina appears to have existed during almost the entire series of Palaeozoic 
and Mcsozoic periods up to the present day ; and it is probable that the animal 
was not at any period the inhabitant of very deep water, for all the recent 
species of Lingula and Discina, or tliose species with a horny shell, have pre- 
vailed in the littoral zone, and do not appear to have descended deeper tliau 
about eighteen fathoms. The reader is referred for more ample details to 
Prof. Suess' adiTiirable "Men^oir on the Habitat and Distribution of the 
Recent and Possil Brachiopoda," recently published in Vienna. 
XLV.— Discina nitida. Phillips. PI. v., figs. 22-29. 
OMcula iiUida. Phillips' "Geol. of York," vol. ii., p. 221, pi. xi., figs. 10-13, 
1836, = 0. c'liida, Portlock's " Report of the Geol. of Londonderry, &c., 
pi. xxxii., figs. 15, 10, 1813, = T). bulla, M'Coy's " British PaliEozoic 
Fossils," pi. md., fig. 32. 
Tlie shells composing this species are marginally circular, or elongated oval, 
the posterior portion being rather narrower than the anterior one. The larger 
or free valve is conoidal, or limpet-Uke, and more or less elevated, the pointed 
apex being situated at variable distances between the centre and the posterior 
margin, but it is not always the most elevated portion of the valve. The sui'- 
faee of the shell is covered with numerous small irregular concentric wrinkles, 
or stria;. The smaller or lower valve is somewhat flattened, or slightly concave 
towards its anterior margin, with an oval-shaped foramen, surrounded by an 
elevated convex margin, which extends from near the centre of the valve to a 
variable distance from the posterior edge. This valve is likewise ornamented 
with numerous small irregular concentric ridges, or wrinkles, with small 
flattened interspaces. No interiors have been hitherto obtained ; while the 
largest Scottish examples I have seen measured ten lines and a-half in length 
by about the same in width, the depth or elevation of the larger valve bemg 
about six lines. 
After a lengthened examination of Discina cincia, as well as of Discina hidJu, 
I could perceive no valid grounds for separating these two so-termed sjiecies 
from D. nitida ; and any one possessing a sufficiently numerous series of specimens 
of the last named form would, I think, soon perceive that Phillips' shell presented 
every degree of elc\ ation — from that of an almost depressed shell to that ex- 
treme " inflated bubble-like form," described by Prof. M'Coy. I am therefore 
quite disposed to concur in the Irish author's opinion when he considers 
I), cincta as nothing more than the perfect condition of D. nitida ; for when the 
outer surface of the last named shell is absent, which is often the case, the cast 
is generally almost smooth, or marked only with a few faint concentric and 
radiating Imes, a circumstance which has apparently led some paleontologists 
to believe that Phillips' shell was smooth, while that of Portlock's was concen- 
trically striated. 
Discina nitida is a common species in certain Scottish localities. It occurs 
at Belston Place Burn, in Lanarkshire, at one hundred and seventy-three 
fathoms below Ell coal ;" two hundred and thirty-nine at Gare ; two hundred 
and sixty-five at Belston Burn; and three hundred and fifty-four at Raes Gill ; 
all in the parish of Carluke * It is likewise found at Haw-hill, near Lesma- 
hago ; Auchentibber and Calderside, High Blantyre ; and Capel Rig, East Kil- 
bride. In Renfrewshire, at Arden-quarry, Thornliebank. In Stirlingshire, at 
Craigenglen ; and in the Balgrocheu Glen ironstone, etc. In Ayrshire, at Craigie, 
near Kilmarnock ; Cessnock, parish of Galston ; and Nctherfield, near Stratli- 
avon. In Eifeshirc, at Strathkenny, St. Andrews, &c. In Haddingtonshire, at 
* Identical spcc mene are found in Pike and Adams county, Ulinoif, America. 
