﻿STRAPAROLLUS. 



319 



Shell depressed, discoidal ; under surface largely excavated, upper surface flat 

 or scarcely concave. The whorls are numerous, narrow, quadrangular, with 

 flattened sides, which in some specimens exhibit more tendency towards contrac- 

 tion anteriorly than in others. The marginal keels are closely tuberculated, the 

 tubercles being rather round and small. These tuberculations are of equal 

 strength on both upper and under surface, but are scarcely connected by costse 

 across the flanks of the body-whorl. The entire shell is richly ornamented by a 

 trellis-work of spiral lines decussating with growth-lines. Aperture quadrangular, 

 the axial diameter considerably longer than the spiral. 



Relations and Distribution. — This beautiful species is easily distinguished from 

 those previously described by the narrowness of the whorls and the peculiar 

 roundness and closeness of the nodes. In the character of the spiral lines it 

 somewhat approaches Discohelix Cofxtvuhliae, but differs greatly both in orna- 

 mentation and the shape of the whorls. To a certain extent our shell resembles 

 8tr. joulchellus, d'Orb. ('T. J.,' ii, p. 312, pi. cccxxiii, figs. 1 — 4), but that species 

 is more depressed, and its whorls are triangular rather than square. 



Strajparollus pulchrior is essentially a fossil of the Murchisonas-zone. I have 

 specimens from Mapperton, Coker, and Bradford Abbas, at all which places it is 

 very rare. Apparently it occurs also at Dundry. 



252. Strapaeollus Dundriensis, Tawney, 1873. Plate XXVI, fig. 2. 



1873. Strapaeollus Dundriensis, Tawney. Dundry Gasteropoda, p. 35 (27), 



pi. ii, figs. 9 a. 9 b. 



Description. : 



Diameter . . . . .18 mm. 



Height . . . . .9 mm. 



Shell depressed, discoidal ; under surface considerably excavated, upper 

 surface nearly flat, or sometimes slightly raised. The whorls are numerous, 

 quadrangular, narrow (spirally), deep (axially) ; the sides are flattened with a 

 considerable amount of anterior contraction as shown in the body-whorl. The 

 tuberculations on the upper marginal keel are very dense and round, and the 

 effect is to raise the keel considerably, and thus produce a sulcation of the 

 rest of the upper surface, which also has about four dotted spiral lines between 

 the rows of tubercles. 



The body-whorl is deep, its height being equal to half the total diameter 

 of the shell, though there is some difference in this respect ; ornamented on 

 the flank with spiral lines, which decussate with curved growth-lines so as to 

 produce a rich reticulate pattern. The upper angle is somewhat less than a right 



