244. W. H. Hudleston—The Yorkshire Oolite. 
least, of the Corallian fossils. For some years I have had a tolerable 
acquaintance with the rich stores of these fossils in the museums at 
York and Cambridge. There is the Bean collection, too, at the 
British Museum. I have myself a fair collection, but, above all, 
Sir Charles Strickland has been kind enough to place at my disposal 
such specimens as may be required from his own collection. This 
last privilege is, indeed, most valuable, for, to say nothing of the 
excellence and variety of many of his specimens, Sir Charles 
has been careful in almost every case to note the locality, and no 
one can vie with him in the art of developing a fossil out of a 
difficult matrix. 
Under these circumstances it has been determined to commence 
with the Corallian Gasteropoda. The principle upon which I would 
proceed is never to make a new species if it can possibly be avoided, 
but to endeavour where necessary to clear up doubts regarding 
species imperfectly figured and described, or else to figure Yorkshire 
specimens of species which have been described elsewhere. All 
specimens whose locality is doubtful will be excluded, nor do I bind 
myself in any way to produce an exhaustive list, or to figure every 
species. Still less do I undertake to define what a “species” is, as 
this would raise questions entirely foreign to the scope of the present 
article, though I am fully aware that what Professor Marsh?’ calls 
the third period in paleontology has long since come to an end. 
To simplify, rather than to multiply, should now be the object of 
the fossil conchologist, but always with a due regard to persistent 
variety of form. In'this way we shall be able to correlate our 
Yorkshire beds more closely with those of the rest of England and 
of neighbouring countries, and thus add a stone to the pile of trust-_ 
worthy information, which, if less interesting as a mode of dealing 
with the subject than the problems of speculative geology, may serve 
to form a sure foundation for legitimate deduction in the future. 
No. 1. Corallian Gasteropoda. 
The details with regard to geological position and localities of the 
species described are to be found in the “‘Corallian Rocks of England,” 
by Blake and Hudleston,? in the “Yorkshire Oolites” (Part ii. 
sections 1 and 2),° and in Mr. Fox-Strangways’ Memoir in Expla- 
nation of Quarter-sheets 95 S.W. and 95 S.E., just published. 
In Part ii. section 2, of the Yorkshire Oolites, there is a full table 
of the Corallian fossils of Yorkshire, together with a chapter on the 
paleontology. The scheme of the Corallian series in Yorkshire 
may be gathered from the accompanying table (pp. 246-247), 
extracted from the last-mentioned publication. The general geo- 
logical features of the district are so well known from the writings 
of Phillips and others, that nothing further need be said on this subject. 
* Address before the American Association for the Advancement of Science, 1879, 
2 Quart. Journ. Geol. Soc. 1877, vol. xxxiii. p. 317. 
* Proc, Geol. Assoc. 1876, vol. iv. p. 3538, and 1878, vol. v. p. 407. 
