256 W. H. Hudleston — On the Yorlishire Oolites. 



Note on Nerita costulata, Deshayes. — Mr. Walford writes : " In 

 your comments in tlie Geol. Mag. on N. costulata, you speak of it as 

 not occurring in the G. 0. I have several specimens from the base 

 of that formation vpith the slight mesial angularity and thickening 

 of the costee j^on quote. One form approaches Nerita rugosa." 



Note on ^' FhasianeUa" latiuscula, Morris and Lycett. — No shell 

 of this " species " has yet been seen by me ; but bearing in mind 

 the very considerable abundance of the so-called " Phasianellce^' allied 

 to JP. elegans in the Lincolnshire Limestone, I have less hesitation 

 in admitting this " species " into the Table of species retained. 



Note as to Cerithium Comptonense. — Owing to some mistake, this 

 species is described as occurring at Conipton. It really occurs at 

 Weldon. The name, however, having been given, should stand. 



Note on Trochotoma calix. — It appears that the specimen figured 

 (Plate IV. Fig. 6) in the April number of the Magazine is regarded 

 at York as the type of Solarium calix, Phil. Therefore the first half 

 of line 1, p. 157, should be cancelled. 



Note on the Table of Fossils. — The accompanying Table in a 

 great measure explains itself. The numbers in the left-hand column 

 refer to the enumeration in the text, and each number usually repre- 

 sents what is deemed a species. The right-hand columns, seven in 

 number, indicate the fossiliferous zones, and the star or letters the 

 occurrence of the species. A few are noted as ascending into the 

 Corallian. The number of representative forms in the Corallian is 

 much greater. 



I have often expressed .the opinion that we must not rely too 

 much on Tables. They are apt to accentuate the palseontological 

 breaks in a given series of beds, and at best are only a somewhat 

 unsatisfactory contrivance for afibrding a synoptical view. At the 

 same time, such a Table as this may be relied upon to indicate how 

 the Gasteropod fauna of the Yorkshire Oolites continued to diminish 

 in richness from the fine start it made in the Dogger, until it be- 

 came very poor indeed in the beds immediately underlying the 

 Coralline. Two species already enumerated in the " Corallian 

 Gasteropoda" should, however, be added to those of column vii, 

 which represents the Lower Calcai'eous Grit. These are (1) Litto- 

 rina muricata, Sow., var. A, which takes the place of Turbo Phillipsi, 

 M. and L. ; and (2) ActcBon retusus, Phil. 



Taking a comprehensive view of the case, and not relying too 

 much on the Table, the results are that a somewhat scanty series of 

 Gasteropoda in the Dogger Sands is succeeded by a really rich 

 Gasteropod fauna in the Dogger. Most of the genera known to 

 occur in the Yorkshire Oolites are well represented on this horizon. 

 The genera conspicuous for their absence or rarity are the so-called 

 " Phasianellas " of the P. elegans type (Pseudomelania), Trochus, and 

 Pleurotomaria. On the other hand, Purpurina, Nerincba, Alaria, 

 Onustus, Neritopsis, and Trochotoma now appear for the first time in 

 the Yorkshire Jurassics. In the case of Nerincca and Alaria these 

 are well represented both in individuals and probably in species : 

 certainly they are in varieties ; but the conditions of preservation 



