﻿LITTORINA. 



295 



four serrated spirals of nearly equal prominence ; in some cases the fourth spiral 

 has a slight salience, and where the suture gapes a fifth spiral without tuber- 

 culations may be detected towards the bottom of the hollow. 



The body-whorl rather exceeds half the height of the shell ; it is slightly 

 angular, and not ventricose ; ornaments as in the whorls of the spire ; base full 

 with about six finely cut spirals. Throughout the shell the interspiral stride are 

 deep, and the serrations of the carinas almost tooth-like and somewhat bent up- 

 wards ; but there is considerable variety in the nature of the ornaments. 



Aperture ovate with a straight pillar lip, in the earlier stage slightly reflexed 

 anteriorly. 



Relations and Distribution. — Our specimen is rather more conical than the 

 one figured by Goldfuss, but there are others which correspond in almost every 

 particular. In younger specimens which are free from matrix intermediate 

 spirals of slight salience may be seen. 



This is a sort of average form, which may be said to inosculate with others in 

 the Jurassic rocks. The abundant Littorina muricata of the Corallians might be 

 regarded as a micromorph on a higher horizon. Some varieties of Amb. Milleri 

 are also near. On the other hand, the euc# cloid varieties approach the ornata- 

 group in many ways. 



Littorina prsetor is rare. My own specimens are mostly from the Murchisonas- 

 zone of Bradford Abbas. There is a specimen in the Woodwardian Museum 

 stated to have come from Dundry. 



The handsome shell, PI. XXIII, fig. 4, may possibly represent a modifica- 

 tion of Lilt, prsetor on a higher horizon, viz. the eoncavus-zone. In most shells of 

 this class the pillar-lip is straight with a considerable deposit of callus. This 

 specimen is the only one I have seen of the kind. 



229. Littorina (Tectarius or Echinella) polytimeta, sp. nov. Plate XXIII, figs. 



12, 1:3. 



Cf. Tubbo Davidsoni, Laube. Gast. braun. Jur. Balin, p. 8, pi. ii, fig. 1, for this 



and the following species. 



Description : 



Length ..... 15 — 20 mm. 

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



Spiral angle .... 62°. 



Shell thick, conical ; spire pointed. Number of whorls about seven, the 

 apical ones being convex and smooth, the remaining whorls nearly flat, and 

 marked off by a channelled suture. The ornaments are peculiar ; they consist of 



