ALARIA. 123 



44. Alaria Roubaleti, Schlumberger, 1864, var. Dorsetensis. Plate V, figs. 5 a, 



5 b, 5 c, 5 d, 5 e, 5 /; and Plate VII, 

 fig. 10. 



1864. Alaria Roubaleti, Schlumberger. Bull. Soc. Linn. Norm., vol. ix, p. 223, 



pi. vi, figs. 4 — 6. 



1867. — — Piette, Cont. de la Pal. Franc., p. 102, 



pi. xx, figs. 4 — 8. 



Bibliography, 8fc. — The typical Alaria Roubaleti, Schlumb., is said to occur in 

 the Department of the Meurthe (Lorraine), in a bed characterised by Am. Sowerbyi 

 and Am. cycloides. The Dorsetshire fossil now under consideration is eminently 

 characteristic of the so-called Sowerbyi-bed of Bradford Abbas, where it is rather 

 abundant, and of course subject to considerable variety. In collections it is 

 generally labelled Al. Dundryensis. 



Description : 



Length of large specimen . . .32 mm. 



Width of body-whorl to height of shell . . 44 : 100. 



Spiral angle . . . . .36°. 



Shell turrited, fusiform, subconical ; apex very blunt. Whorls about ten ; 

 apicals globose and smooth, succeeding whorls convex, and becoming angular 

 owing to the development of a strong keel, which is rather below the middle. The 

 longitudinal costas of the earlier whorls of the spire are very numerous, curved, and 

 extend from the posterior almost to the anterior suture. These costge disappear 

 entirely on the posterior area of the ante-penultimate, and are only traceable as 

 very faintly-cut serrations at wide intervals on the penultimate. The spiral lines 

 are fine and very numerous ; in the posterior areas they are closely set and of nearly 

 equal strength ; anteriorly the spiral lines are more irregular, so that a shallow 

 sulcus is formed between each keel and the anterior suture. 



In immature specimens, which have not developed a wing (fig. 5 e), the last 

 whorl is strongly bicarinate, but the next half-turn, which developes the wing, 

 presents a body- whorl with the anterior keel greatly diminishing in importance as 

 it approaches the margin. In mature specimens the body- whorl is full, entirely 

 without longitudinal ornament, and only slightly bicarinate ; the spiral lines are 

 fine and very numerous, and slightly cross-hatched by radial lines of growth. The 

 posterior keel carries two very powerful spinous processes (see basal views of figs. 

 5 a and 5 c) ; the anterior spine, a, is a quarter of a turn above the wing ; the 

 posterior spine, p, is a quarter of a turn farther back, and, consequently, opposite 

 the wing ; both spines curve forwards. 



