54 MOLLUSCA FROM THE GREAT OOLITE. 
Shell small, turbinated, acute; whorls very convex, and thrice carinated; carine 
crenulated, the upper one placed near to the suture; the others about the middle of the 
whorl, and near together; the last whorl has near to its base very fine encircling lines; the 
aperture is small, and nearly orbicular. 
In this minute shell the largeness and roundness of the carinz, and the great convexity 
of the whorls are the most prominent features. 
Locality. We have procured two specimens from the white stone of Bussage ; but in 
this, and probably other instances of minute shells, the small number known may indicate 
rather our defective observation than the true relative numbers which they present. 
Rissomna? avis, Sow. Plate IX, fig. 16. 
Rissoa L&vis, Sow, 1829. Min. Con., t. 609, fig. 1. 
_— — Brown. LIIlust. Foss. Conch., p. 79, t. 38, fig. 12. 
_— —  Bronn. Index Paleont., p. 1092. 
R. Testé parva, turrita, levi, subcylindricd; anfractibus (6) subplanatis; anfractu 
penultimo, et ultimo subcylindrico; aperturd parvd, obliqud. 
Shell small, turreted, pomted, smooth, and subcylindrical ; whorls (6) rather flattened ; 
the last whorl, and also the penultimate whorl, are nearly cylindrical ; aperture small and 
oval, oblique. Length 23 and 3 lines. 
Locality. Ancliff; also very rarely at Minchinhampton Common, where it has been 
found in the planking. 
This species scarcely exhibits the anterior notch characteristic of Rissoina. 
Pacopus, Gray. 
Sub-genus—AMBERLYA. 
P. Testa turritd, turbinatd, apice acuto; anfractibus superneé planis, infra convexis et 
nodulatis; anfractu ultimo ventricoso; apertura ovatd, integrd, labio interno calloso umbih- 
cum via obtigente; suturis profunde impressis; columella nulla. 
Shell turreted, turbimated, apex acute ; whorls flattened above, convex, and nodulated 
beneath, the last whorl ventricose ; aperture ovate, entire ; inner lip thickened, and nearly 
covering a small umbilicus ; sutures deeply impressed ; no columella. 
The whorls are received into the concavity of those which succeed, the latter at their 
junctions being slightly overwrapped by the former, after the manner of Scalaria; the 
aperture is oval and oblique; the outer lip thin; the figure varied somewhat according to 
the stage of growth, the last one or two volutions in adult specimens becoming more tumid 
than the others; in such examples, therefore, the spire acquires a slightly concave figure. 
