THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE III. VOL. I. 



No. IV.— APRIL, 1884. 



OK,IC3-I35r^^Xj J^I^TIGLES. 



I. — Contributions to the Paleontology of the Yokkshiee 



Oolites. 

 By Wilfrid H. Hudleston, M.A., F.G.S. 



(Continued from Decade III. Vol. I. p. 115.) 



(PLATE VT., excepting Figs. 11 and 11a.) 



Genus Alaria, Lycett, 1850. 



S in the case of Nerincea, so also in this genns, we are dealing with 



A 



its earliest representatives in so far as this district is concerned, 

 since Tate and Blake make no mention of the occurrence of Alaria 

 in the Yorkshire Lias. Piette, who accepts with modification 

 Morris and Lycett's genus for this section of the winged shells, is of 

 opinion that no truly winged shell has ever been found in the Lower 

 Lias of France, though he describes species from the Middle and 

 Upper Lias, none of which, according to his views, pass upwards. 

 It was in the Lower Oolites that the genus Alaria first began to 

 flourish, and we find in most places that it became tolerably well 

 represented as low down as the Inferior Oolite or Bajocian sub- 

 division. 



The following are the principal generic characters of Alaria as 

 defined by Piette (Pal. Frang. Terr. Jur. iii. p. 16) in the continua- 

 tion of the Paleontologie Franyaise. Want of sinus, absence of 

 posterior canal, slight importance of the columellar callosity ; the 

 form of the wing finger, separated alike from the canal and the 

 first whorls of the spire ; the nakedness of the first whorls, which 

 are smooth and convex, the keel on the later ones : lastly, the power 

 of developing varices, spurs, and protuberances at various periods 

 of increase — evident traces of rudimentary wings, which appeared 

 usually on the side opposite the actual (definitive) wing. 



Compared with other districts the Yorkshire Oolites cannot be 

 said to be very rich in species of Alaria, or of the allied genera, such 

 as Chenopus, Pterocera, etc. This poverty may be partly due to the 

 imperfect preservation of specimens, whereby the small differences 

 which are held to separate species cannot be made out with certainty. 

 Thus in the " Corallian Gasteropoda " I only ventured to record 



DECADE III. — VOL. I. — NO. IV. 10 



