J. Star Me Gardner — On the Gault Aporrhaidce. 55 



nearly a right angle to the axis of the spire. The aperture is 

 oblique and pyriforrn. The lower portion of the last whorl may 

 sometimes be longitudinally ribbed ; on the first whorls the posterior 

 median keel predominates more or less to the exclusion of the others. 

 The shell without canal measures '033, the canal '045, wing process 

 •045, middle digit -024. 



Distribution. — This is a very characteristic, and I should think 

 will prove a widely distributed, though rather rare shell. It is 

 found in the Lower Gault at Folkestone, and in Switzerland, at 

 Sainte-Croix, the Perte-du-Ehone, and also in France, at Dieuville, 

 Colombieres. It cannot be confounded with any other species. 



History. — Pictet and Eoux first described this species in 1849 in 

 the Moll. foss. Gres-verts, p. 261, pi. 25, fig. 7, from the Gault of the 

 Perte-du-Ehone. Their specimens were all casts. D'Orbigny in- 

 cluded it in his Prodrome, and Pictet and Eenevier found it, 1854, 

 in the Gault of the Perte-du-Ehone. Pictet and Campiche in 1864, 

 pi. 94, figs. 10 and 11, p. 617, figure a specimen from Folkestone, 

 and casts from Sainte-Croix. In 1865 Tate described it in the 

 Geol. Eepert. p. 96, fig. 16 ; and in 1869 Jaccard mentions it from 

 Sainte-Croix. 



Type: — Aporrhais Grtffithsii, Gardner. PI. III. Figs. 11-14. 



Description. — Shell elongated and pupasforru, composed of eight 

 very convex whorls, the last having a less diameter than is required 

 to form a regular cone. The whorls have a central, salient, angular 

 keel, and a second anterior keel conceals the suture ; there is also a 

 third and faintly marked keel anterior to the predominant one and 

 midway between it and the suture. The keels are not visible in the 

 first two or three whorls, but develope as they increase in size, all three 

 keels being visible on the last and penultimate whorl. The whorls, 

 except the last two, are ornamented with fine, transverse, oblique, 

 acute, and angular ribs, wide apart, eight or nine on each whorl, 

 which interrupt the median keel in crossing and form nodose tuber- 

 cles. This ornamentation is most distinctly seen near the apex, 

 where the keels are obsolete, and becomes less so in descending the 

 spire. The last whorl is smoothly striated, having the three keels 

 pronounced. The principal keel is prolonged into a narrow acutely 

 angular process at right angles to the axis, till near its termination, 

 where it curves gradually upwards, terminating in a fine point. A 

 straight downward spike seems to correspond with the second keel. 

 The anterior canal is longer than the spire, and is recurved abruptly 

 to the left, as in A. cingulata. The aperture is narrow and angular, 

 without encrustation. 



In form this species bears a striking similarity to A. cingulata, 

 with which I have grouped it ; but the ornamentation is of a dif- 

 ferent character and the shell is much smaller. Its sculpture strongly 

 resembles that of B. tricostata, D'Orb., Pal. Fr., pi. 207, fig. 5, 

 p. 287, from the Gault of Ervy, where it is rare, and A. triboleti, 

 P. and C., from the Lower Aptien of Sainte-Croix. The keels are, 

 however, in these latter strongly marked near the apex, and the 



