﻿278 



GASTEROPODA OF THE INFERIOR OOLITE. 



species, was subsequently named by Lycett (Suppl., p. 19) Amberleya Jurassi, Lyc. 

 This name is regarded by Cossmann (' £t. Bathonien,' p. 243) as a synonym of 

 Amberleya (Turbo) Castor, d'Orbigny. In the Addenda to the Supplement Lycett 

 refers a small form from the Forest Marble of Laycock and Pound Pill to 



Amberleya capitanea. We may perhaps regard this as a case of atavism. 



Description : 



Length of full-grown shell . . . 30 — 35 mm. 



Length of body-whorl to total height . . 50 : 100. 



Spiral angle .... 55°. 



Shell eucycloid, turrited. Whorls about seven, angular, narrow, and sloping 

 outwards from the suture ; sutural space wide. 



In the whorls of the spire the ornaments consist of two centrally situated 

 tubercular spirals forming a double belt ; the cross-hatchings are fine and 

 numerous, and fill up the interspiral spaces. The body-whorl is large, and the 

 sides are similarly ornamented ; in the base are four or five less prominent 

 spirals, with tuberculations gradually diminishing in size anteriorly ; cross- 

 hatchings numerous. 



Aperture ovate, with a tendency in the columellar lip to be produced 

 anteriorly ; outer lip thin and crenulate. 



Relations and Distribution. — The differences between Amberleya capitanea and 

 the numerous varieties or sub-species more intimately allied with Amberleya, 

 ornata are slight, but they are fairly constant, and occur for the most part on a 

 certain horizon. The spinulose varieties of Amb. ornata are very near indeed, 

 but they may be always distinguished by the presence of a third circlet of small 

 tubercles on the upper margin of all the whorls, this circlet being less prominent 

 than the other two, and also by the more elongate form of the tubercles, which 

 in Amb. cajntanea are very round. 



Amberleya capitanea is interesting as the earliest member of the ornata-groxxp 

 in the British Jurassics. A fairly good specimen is figured by Mr. Beeby 

 Thompson from the Lower Cephalopoda-hed at Preston Capes. This is presum- 

 ably from the Serpent inns-beds, and is the earliest occurrence of which I have any 

 knowledge, though there are other instances in the Upper Lias of the Midlands. 

 In Dorsetshire, according to Moore (' Mid. and Up. Lias, S.W. England,' p. 78, 

 pi. vi, figs. 1 — 4), Amb. capitanea occurs characteristically along with Amm. bifrons 

 and Amm. communis in the Upper Lias at Compton. 



The evidence in England is thus distinctly in favour of this being regarded as 

 a Toarcian species, as had been already indicated by d'Orbigny for France. 

 Moore (loc. cit.) goes on to say that on the uppermost horizon of the Upper Lias 

 in the Cottes wolds Amb. capitanea occurs along with Amm. variabilis, &c. This is 

 the horizon and locality whence comes the specimen figured in the present work. 



