ALARIA. 133 



describes three varieties of Al. Lorieri. His third variety, which occurs in the 

 " Oolithe ferrugineuse " of Bayeux (op. ciL, pi. ii, figs. 12 — 14, and pi. iii, figs. 11, 

 12), might be expected to have most resemblance to our Dorsetshire specimens. 

 There are differences in the Dorset-beds but they do not correspond, in all cases 

 to the differences indicated by Piette. Viewed broadly we may say that the 

 trifida-grouip is represented in the Inferior Oolite by a series of fossils which in 

 France are recognised for the most part as Al. Lorieri, and in Germany as 

 Al. (Chenopus) Philippi. Each of these has its own set of synonyms, and some 

 English palaeontologists would designate the whole as Alaria trifida. 



Without doubt the Burton-Bradstock fossils must be regarded as representing 

 the Al. Lorieri of common repute, though possibly not exactly the Al. Lorieri 

 of D'Orbigny. Three varieties are shown in the accompanying plate, and these 

 I proceed to describe. 



Var, A. (Figs. 6 a, 6 b, 6 c.) 



Description : 



Length . . . . .20 mm. 



Width of last whorl to height of shell . . 45 : 100 



Spiral angle . . . .35° 



Shell fusiform, sub-turrited. Whorls nine ; apex moderately blunt ; apical 

 whorls tumid without keel or ornament ; the five succeeding whorls of the spire 

 are strongly carinate ; the carina is median, and in well-preserved specimens is 

 seen to be characterised by a furrow. (This is one of the distinctive features of 

 Al. Lorieri according to Piette). There are no longitudinal ornaments, but the 

 spiral lines are regular and conspicuous, being most numerous on the posterior 

 area of each whorl ; in the anterior area is a sulcus immediately above the suture, 

 and in the middle of this sulcus is a fine thread-like line, most obvious on the last 

 three whorls ; a rim is exposed at the base of the lower whorls, and the suture 

 rather gapes in consequence. The body-whorl is strongly bicarinate, the posterior 

 keel, representing the median carina of the spire-whorls, being the most salient. 

 It gives rise to the posterior digitation (fig. 6 b) which rapidly attenuates in 

 describing a curve, whose centre is a point some little way beyond the apex of the 

 shell. The wing is slightly palmate, the intercarpal space being slightly excavated 

 and. spirally striated. The anterior digitation, although arising from the least 

 salient keel, becomes wide and bayonet-shaped for a short distance, and after 

 developing a broad, tongue-like process, curves slightly upwards to its blunt 

 termination (fig. 6 a). 



