ALARIA. 123 
44, Avaria Rousatyti, Schlumberger, 1864, var. Dorsrrensis. Plate V, figs. 5 a, 
5b, 5c, 5d, 5e,5 f; and Plate VII, 
fig. 10. 
1864. Atanta Rovusaxert, Schlumberger. Bull. Soc. Linn. Norm., vol. ix, p- 223, 
pl. vi, figs. 4—6. 
1867. — — Piette, Cont. de la Pal. Frang., p. 102, 
pl. xx, figs. 4—8. 
Bibliography, §c.—The typical Alaria Roubaleti, Schlumb., is said to occur in 
the Department of the Meurthe (Lorraine), in a bed characterised by Am. Sowerbyt 
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 : . 32mm. 
Width of body-whorl to height of shell . . 44: 100. 
Spiral angle . ‘ : 30 
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 costze of the earlier whorls of the spire are very numerous, curved, and 
extend from the posterior almost to the anterior suture. These coste 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. 
