76 MOLLUSCA FROM THE GREAT OOLITE. 
PHASIANELLA TUMIDULA. Plate XI, figs. 25, 25a. 
P. Testa turbinatd, elongata; spird acutd; anfractibus convexis (8), suturis depressis ; 
anfractu ultimo globoso; aperturd magna ovato-rotundatd. 
Shell turbinated, elongated; spire acute; whorls (8) convex, the sutures deeply 
depressed ; the last whorl globose ; the aperture large, ovately rounded. 
This species has an elevated, acute spire, and convex whorls, and is remarkable for the 
sudden increase of the last two volutions, which are very ventricose. Neither of our 
specimens are quite perfect about the outer lip; but the distinctive character of the species 
is sufficiently evident. Axis 19 lines, transverse diameter 11 lines. 
Locality. It occurs rarely in the planking at Minchinhampton Common. 
Family—PLEUROTOMARIDE. 
Pixvrotomaria, Defrance. 1825. 
ScrssurELLA, D’Orbigny. 1823. 
Shell turbinated or conical; aperture subquadrate, the angles rounded; outer lip thin 
and sharp, having a fissure or deep notch m the middle part, or near to the suture; an 
encircling band or rib round each whorl follows the fissure. 
The Pleurotomarié are rare in the Minchinhampton beds, and the larger specimens are 
usually broken. It will be observed, in the following descriptions, how very few examples 
of each species have been obtained, so that we are almost enabled to give their number 
with exactness. Placed amidst such a multitude and variety of molluscous relics, in spots 
teeming with life, it is not easy to account for their rarity and imperfect condition. 
Inferring that they were usually gregareous, we are led to suspect that the “¢tora/ condition 
of these shelly beds was not suited to their propagation, and that the larger imperfect 
specimens were denizens of greater depths, the shells occasionally being stranded among 
the more littoral Mollusks. As a remarkable instance of the recurrence of similar phe- 
nomena at a very distant locality, we would direct attention to the elaborate and valuable 
Memoir of M. Deslongchamps,' on the P/eurotomarie of the secondary formations of 
Calvados, in which 53 species are mentioned as occurring in the Lias and the Lower and 
Middle Oolitic systems. It is stated that they are exceedingly abundant ; but, on referring 
to the Great Oolite species, 11 in number, we find, with one exception only, a repetition 
of the following remarks appended to them: “One example; two examples; rare; very 
rare.” In fact, when describing the species which we have identified in that Memoir, we 
seem, when stating their numbers, to be repeating the words of its author. 
1 Mem. Soe. Linn. de Normandie, vol, vii. 
