126 GASTEROPODA OF THE INFERIOR OOLITE. 



Description : 



Probable length . . . .40 mm. 



Width of last whorl to length of shell . 25 : 100. 



Spiral angle . . . .14°. 



Shell extremely elongate, slightly turrited. Whorls about ten (six visible in 

 the figured specimen), convex, and scarcely angular, since the very slight keel or 

 shoulder is close to the anterior suture. The longitudinals consist of regular and 

 very straight ribs of considerable thickness, extending nearly from suture to 

 suture ; these decussate with a system of rather prominent spirals, which are con- 

 tinued in the base of the shell. The body-whorl shows a slight increase beyond 

 the regular spiral angle, owing to the development of a strong median keel. 



Piette observes that this keel, which becomes spinous on the side opposite the 

 wing, forms in its prolongation a thick digitation bent upon itself, which twists 

 towards the point of the spire. 



Relations and Distribution. — This is a Monodactyl of peculiar form, which seems 

 almost to stand by itself, or at least to have no near relations, except perhaps in 

 some degree to the species next described. Piette describes several varieties. 



It is said to be common in the zones of Am. Sowerbyi and Am. Murchisona, in 

 the Department of the Meurthe. The Dundry specimen now figured, originally 

 described by Tawney, is at present unique as a British example of this species. 



48. Alaria pr^elonga, sp. nov. Plate V, fig. 10. 



Description : 



Probable length . . . .46 mm. 



Width of body-whorl to length of shell . 30 : 100. 



Spiral angle . . . .17°. 



Shell extremely elongate, turrited. Whorls ten or eleven in number, and 

 moderately angular, the keel being situate rather more than one-third the distance 

 from the anterior suture. The longitudinals are mainly confined to the anterior 

 area of the whorls, and consist of very straight stout costse, decussating with 

 spirals which are more or less obliterated in the available specimens. In the 

 penultimate the longitudinals fail entirely, the keel being plain and nearly median. 

 There is a sharp rise of the keel in the body-whorl, which keel is also plain with 

 indications of a spinous projection on the side opposite the outer lip ; the position 

 of the keel is irregular. 



The aperture is triangular, and there is a considerable callous deposit on the 

 columellar side. The indications of a wing and canal are not distinct. 



