250 Mr. J. Lycett on the Fossil Conchology of the 



conchology and their good state of preservation. Here at one 

 locality we find a large assemblage of a genus which seems to be 

 characteristic of this formation and especially of this vicinity ; I 

 allude to the new genus Purpuroidea (see the figures), of which 

 the generic characters are as follow : — 



Shell turreted, ventricose, aperture large, apex of the spire 

 pointed. Spire consisting of several whorls usually convex, and 

 having about their middle part a circle of tubercles or blunt 

 spines. Columella smooth, rounded, and curved inwards at its 



Purpuroidea nodulata, middle size. 



Notch wide, but not deep nor recurved. Outer lip thin, 

 slightly sinuated, and forming an acute angle posteriorly at its 

 junction with the body whorl. The casts of the interior are 

 smooth, or exhibit but faint indications of the tubercles, and 

 none of the ribs or striae which distinguish the perfect shells. 

 The axial umbilicus is usually very conspicuous and the basal notch 

 not distinguishable. They would certainly be taken for Naticce 

 by persons not conversant with the outer form, and even appear 

 to have been figured as such by Roemer under the title of Natica 

 subnodosa from the oolite of Hanover. One of the species has 

 twice been imperfectly figured in English works ; first in Young 

 and Bird's ' Geology of the Yorkshire Coast ' as Murex nodulatus ; 

 the figure is merely a rude sketch of a bad specimen, but charac- 

 teristic ; subsequently a figure representing little more than a 

 cast was given in the ' Mineral Conchology ' as Murex tuberosus. 

 The varieties of form and markings which two of the species 

 exhibit are worthy of notice : the most abundant shell, P. rugosa, 



