290 W. H. Hudleston—The Yorkshire Oolite. 
naticoid casts of this shell are common enough, there must have 
been plenty of specimens showing the wide basal notch which 
clearly brings the species within the Siphonostomata. It affords, 
moreover, an instance, happily rare amongst British paleontologists, 
when an author, on the strength of having changed the genus, 
appends his own name to the species. 
In 1850 Lycett! described three species of Purpuroidea from the 
Great Oolite of Minchinhampton, and these three species are ex- 
tremely well drawn by Bone.’ The third of these was identified 
with the Yorkshire form, and received the name of Purpuroidea 
nodulata. It is quite likely that the learned authors of the Great 
Oolite Mollusca were unable to obtain decently preserved specimens 
of our Coral Rag species, or they would scarcely have placed the 
two under the same specific designation. We owe, however, to 
Morris and Lycett the recognition that Murex nodulatus, Y. & B., 
and I tuberosus, Sow., should be classed under the new genus 
Purpuroidea, and thus the mistake of Phillips as to the genus was 
rectified. That P. nodulata, M. & L., is more closely related to the 
Yorkshire shells than are the other two Minchinhampton species 
none will doubt ; perhaps it may be entitled to rank as an ancestor. 
Of course it must be admitted that where one man sees a species 
another only sees a variety ; but in this case the general type of 
ornamentation (and, to a certain extent, also the form) of the Great 
Oolite shell differs materially from any of those found in the Coral 
Rag of Yorkshire. 
In 1852 Buvignier,? who includes. these shells under Purpura, 
takes the opportunity of pointing out the important differences 
between his Coral Rag species, P. Lapierrea (a nearer relation to 
some of the Yorkshire shells), and the Minchinhampton shell called 
P. nodulata by Morris and Lycett. In 1875 Phillips, in his third 
edition, avoiding his original error of calling the Yorkshire shell 
Natica nodulata, Phil., fell into the opposite error of referring it to 
P. nodulata, M. & L. 
Description.—It is not easy to select a typical specimen. Owing 
to original variety of form, aided by some difference in mineraliza- 
tion, and varying degrees of preservation, no two specimens are 
alike. The best plan, therefore, is to give a brief description of 
each of the three shells selected, pointing out the resemblances and 
contrasts, and thus obtain a kind of average diagnosis which may 
serve as a general description. 
Fig. 1.—Specimen from the Coral Rag of Langton Wold (Yorksh. 
Phil. Soc.). 
Teeniptily, oie jecsiadas why spasteveiekies ele aie settee 77 millimetres. 
Bixtremegwidth 2s S.facicrrelcck «lied clots) silsierr 58 yy 
Length of body-whorl to entire shell .......... 71: 100. 
Sle MAD, pogudododcauouqacn e090 odd cdbe 78°. 
Shell turrited, angular, consisting of five or six whorls; ornaments 
of the early whorls, if any, effaced. Penultimate whorl provided 
with about nine stumpy tubercles or studs; suture strongly marked. 
1 Op. cit. 2 Plates v. and vi. 3 Stat. Geol. etc. de la Meuse, p. 44. 
