PLEUROTOMARIA. 409 



Relations and Distribution. — The specimens referred to PI. scrobinula occur for 

 the most part in the Parkins on l-zone, where they are by no means abundant. The 

 one figured is from Woolston. The agreement with Deslongchamps' description is 

 substantial, though he describes PI. scrobinula as having a smooth base — a 

 feature possibly due to wear. 



Fig. 2 represents a specimen from the Cadomensis-hed, Clatcombe (top of the 

 Humjihrlesianus-zone), where the spire is rather more convex and the whorls 

 slightly undercut, and the sinus-band is broad and with little apparent ornament ; 

 there is no umbilicus whatever. This may be a variety of PI. scrobinula, but the 

 ornamentation is rather coarser. In fact, this shell seems to occupy a position 

 between PI. Dundriensis and PI. scrobinula. 



345. Plkurotomaria Alcyone, d'Orbigny, 1850. Plate XXXV, figs. 4, 4 a, 4b. 



1S50. Pleurotoiiaria Alcyone, d'Orbigny. Prod., i, p. 268. 

 1854. — — Terr. Jur., vol. ii, p. 488, pi. 



ccclxxxix, figs. 6 — 10. 

 Description : 



Height . . . . .20 mm. 



Basal diameter . . . .23 mm. 



Spiral angle ..... 73°. 

 Shell conical, trochiform, moderately umbilicate. Spire regular. Whorls 

 (seven) subconvex, with a slight belt developed at the base of each. Spiral 

 ornaments fine throughout, but strongly reticulate from oblique radii in the 

 posterior area of the whorls. 



The sinus-band is submedian, rather narrow, and slightly sunk ; carries one 

 central spiral crossed by growth-lines, is sometimes smooth. The body-whorl is 

 angular at the periphery, subconvex, and has the ornamentation subdued, the 

 base being almost smooth ; umbilicus small and rather steep, with curved radii 

 springing from the margin. Aperture subrhomboidal and depressed. 



Relations and Distribution. — The figured specimen, from the Parlcinsoni-zone of 

 Burton Bradstock, answers well to the description and figures of PL Alcyone in 

 the ' Terrains Jurassiques.' It is rare. 



346. Pleurotomaria Athulia, d'Orbigny, 1850. Plate XXXIV, fig. VI. 



1850. Pleurotomaria Athulia, d'Orbigny. Prod., i, p. 269. 

 1854. — Terr. Jur., vol. ii, p. 4S9 : pi. 



ccclxxxix, figs. 11 — 16. 



