THE 
GEOLOGICAL MAGAZINE. 
NEW, (SERIES? «.BECADE) H...2VOL. Vik. 
No. VII—JULY, 1880. 
OmELGEN AT: AR rEciri mS: 
eR eal? 
I.—ContrIBurions TO THE PALMONTOLOGY OF THE YORKSHIRE OoLtITEs.! 
Part II. 
By Witrrip H. Huprxston, M.A., F.G.S., V.P.G.A. 
(PLATES VIII. & IX.) 
Genus PurpurorpsEa, Lycett, 1848. 
Whatever may be the precise biological value of this genus or 
subgenus as distinct from Purpura, it forms a remarkable group, 
limited, according to our present knowledge, both in time and space. 
Of the conditions favourable to its development we only obtain 
glimpses here and there. In the Coral Rag of Yorkshire one would 
say that the genus displays a remarkable tendency to variability 
within certain limits, so much so that almost every specimen found 
in anything like a decent state of preservation differs in some point 
of ornament: hence the extreme difficulty of specific arrangement. 
One might almost suppose that, like the Ammonite, the genus 
having worked out the limits of possible change, flourished within 
a short period only, and speedily became extinct. 
D’Orbigny’s genus Purpurina, with which this one has been con- 
founded by Buvignier, and even by Morris and Lycett,? should be 
confined to a group of much smaller shells if we accept the limita- 
tions of Deslongchamps,? who breaks up D’Orbigny’s genus into 
Purpurina, Brachytrema, and Purpuroidea. 
1.—PurpuROIDEA NopuLATA, Young and Bird, 1828. Plate VIII. 
Figs. 1, 2, and 4. 
Buceinun, like flammewm, Dillwyn, Young and Bird, Geol. Surv. of the Yorkshire 
Coast, 1822, plate xi. fig. 3, and p. 242. 
Murex nodulatus, Young and Bird, 1828, op. cit., plate xi. fig. 3, p. 244. 
Bibliography, ete.—The figure of this very variable species given 
in the earlier edition of Young and Bird is by no means an 
unhappy attempt. Though little more than a rough sketch, it is 
very characteristic of an average of specimens. The figure in the 
edition of 1828 is inferior. Buccinum, too, was much nearer the 
mark than MMurew, affording one of many instances that the paleon- 
tology as well as the plates of the second edition were inferior to 
that of the first. In his edition of 1835 Phillips calls this species 
Natica nodulata, Phil., identifying it in his reference column with 
Young and Bird’s shell. The change of genus was unfortunate, and 
is the more remarkable from the fact that, although imperfect 
1 Continued from the June Number, p. 248. 
* Mollusca of the Great Oolite, p. 25. 3 Bull. Soc. Linn. Norm. vol. vy p. 119. 
DECADE II.—VOL. VII.—NO. VII. 19 
