S8 NOTES ON THE BRITISH JURASSIC BRACHIOPODA. 



more or less covered with spines, some of whicli, as in 

 A. spinosa, attain a great length. 



Prior to the publication in 1889 of Messrs. Buckman and 

 Walker's Memoir on Acanthothijris, only three species and 

 one variety had been recorded, viz. A. spinosa, crossi, and 

 panacanthina — mistaken by Davidson and other English 

 paloeontologists for A> senticosa, Schl. sp. — all from the 

 Inferior Oolite, and A. spinosa, var. hradfordensis, from the 

 Bradford clay of Bradford-on-Avon, etc. 



To this number they added: — 



A. spinosa, var. ohornensis, B. and W., Inferior Oolite. 



A. ,, ., powerstockeiisis, B. and W., Fuller's Earth. 



A. paucispina, B. and W., Inferior Oolite. 



A. ,, var. cortonensis, B. and W., Inferior Oolite. 



A. tenuispina, Waagen, Inferior Oolite. 



A. senticosa, Schl., var. Jileyensis, B. and W., Lower Cal- 

 careous Grit and Passage beds (3).* 



A. spinosa is the most prolific of the species. Wherever 

 the Upper Trigonia-grit is exposed in the Cotteswold range 

 of hills it is exceedingly abundant, but as we travel in a 

 south-westerly direction through the counties of Somerset 

 and Dorset it becomes, in comparison, rare. On the other 

 hand, A. panacanthina, which is often found in Dorset and 

 Somerset, is exceptionally rare, if not altogether absent, in 

 the Cotteswolds. 



It may be mentioned that Davidson strongly deprecated 

 the generic separation of the spinose from the non-spinose 

 Rhynchonellse. 



In the geological series AcantJwthyris is apparently con- 

 fined to the Oolitic rocks. A living specimen has, however, 

 been found in Japanese waters, A. doderleini, Dav. This is 

 preserved in the Strassburg Museum. 



* Vide Appendix. 



