112 GASTEROPODA OF THE INFERIOR OOLITE. 



The last whorl is somewhat inflated, and similarly ornamented. There are 

 indications that possibly another whorl may have been broken off. 



In the paucity and thickness of its longitudinals, this form bears some resem- 

 blance to Al. rarispina, Schlumb. In order to avoid a mistaken identification I 

 would suggest the name crassicostata as provisional. A single specimen in the 

 Dogger. 



30. Alaeia ? sp. nov. Plate IV, fig. 4. 



The spiral angle is about 30°, the length of the specimen about 20 mm., and the 

 number of whorls ten. The whorls of the spire are short and strongly turrited. 

 The sculpture is rich, the longitudinals being numerous and stout, but somewhat 

 irregular ; they are mainly confined to the lower part of the whorls, and are 

 extremely nodular at the junctions with the spirals. There is no very salient keel, 

 but the anterior portion of each whorl is marked by three coarse spirals, the upper- 

 most of which serves as a keel, and above this are from three to four fine wavy 

 spirals. The body-whorl is similarly ornamented, but shows rather more irregu- 

 larity. It shows no sudden increase. 



Since the specimen is unique and imperfect as regards the aperture, but little 

 can be said by way of comparison. The rich and nodular character of the sculpture 

 seems to separate it from all forms of the hamus-group, and, supposing the 

 shell to be complete in that case the body- whorl is totally different. It was found 

 in the shell-bed of Horton Hill corresponding to the Upper Trigonia-grit (base 

 of ParJcinsoni-zone), and may be known temporarily as Al. Hoetonensis. 



The Hamus-Gcroup. 



A very considerable portion of the more strongly turrited and costate Alaria 

 belong to this important group, which is eminently characteristic of the Monodactyl 

 section. They occur principally in the Upper Division of the Inferior Oolite, at 

 least in the South of England. The forms which most nearly resemble the typical 

 specimens of the Bayeux-beds are to be found chiefly in the Parkinsoni-zone of 

 South Dorset, but micromorphs and varieties, such as Al. Phillipsii, occur in many 

 parts of the Inferior Oolite. Also there are doubtful fossils such as Al. " spinulosa," 

 which may be immature individuals of AL Phillipsii, or, more probably, of Al. 

 unicarinata. 



