﻿320 



GASTEROPODA OF THE INFERIOR OOLITE. 



angle ; its edge (upper marginal keel) is ornamented with numerous sharpish 

 tubercles, decussated by spiral lines. The lower marginal keel is also provided 

 with a number of sharp tuberculations set like a ring round the umbilicus. 

 Ornaments of the lower or umbilical surface uncertain, though there are 

 indications that they bear considerable resemblance to those of the upper surface. 

 Aperture quadrangular, the axial diameter longer than the spiral. 



Relations and Distribution. — The great depth of this shell, irrespective of its 

 peculiar ornamentation, separates this species readily from any previously de- 

 scribed in this work. 



The best and most characteristic specimens are from Dundry. A variety 

 occurs at Stoford, most probably in the Murchisonse-zone. I also possess five 

 specimens in a matrix similar to that of the Murchisonas-zone at Coker, and there is 

 one specimen belonging to the Jermyn Street Museum from the same locality. 

 Altogether about a dozen specimens are known to me. 



253. Straparollus exsertus, sp. nov. Plate XXVI, figs. 3 and 4. 



Description : 



Diameter . . . . .20 mm. 



Height excluding spire . . . .8 mm. 



Height including spire . . . .13 mm. 



Shell depressed, subdiscoidal, widely umbilicate. Spire rather oblique, 

 slightly trochoid, and sometimes equal to about one-third the entire height. 

 Number of whorls about seven, narrow, subquadrangular, and arranged in steps. 

 The tuberculations on the upper marginal keels are large, pointed, and wide apart, 

 the tuberculations being drawn out spirally. 



The upper angle of the body-whorl is nearly a right angle, but the flank is 

 rapidly pinched in towards the anterior marginal keel so as to produce a subtrigonal 

 shape of the whorl. The ornaments of the base or umbilical area are not known 

 for certain, except that the edge of the umbilicus formed by the lower marginal 

 keel is tuberculated. The aperture is quadrangular, the axial diameter being the 

 longest, and the outer lip is somewhat produced anteriorly. 



Relations a,nd Distribution . — This species forms a step in the direction of Solarium. 

 The bold and rather widely spaced tuberculation separates it from those varieties 

 of Sfr. Dundriensis where the spire is somewhat salient. Of the forms previously 

 described in this Monograph, the nearest in ornamentation and in the narrowness 

 of the whorls is Sir. pulchrior, but in that species the whorls are square rather than 

 subtrigonab and not nearly so deep, whilst the upper surface is always flat. 



