Prof. W. B. Benham — A Giant Fossil Cirripede. 115 



in form ; the longer axis is median, and the shorter axis much nearer 

 the broader end. One end of the plate is sharply pointed, while 

 the opposite angle is much more obtuse. 



The valve is arched in the longitudinal direction, and is markedly 

 convex from side to side ; at the broader end a distinct but low 

 keel occupies the median line. 



The surface is marked by closely set lines of growth angulated 

 in the middle line, the angle being directed towards the broader end. 



mm. 

 Length of rostrum ... ... ... ... ... ... 45 



Greatest breadth ... ... 13 



(d) Om of tie Lateral Valves. (PL X, Figs. 10-11.) 



One of the valves, which at a first glance somewhat resembles 

 the apex of a scutum, is doubtless one of the series of lateral plates, 

 very probably the ' upper latus.' Unfortunately it is imperfect, 

 but so much of it remains that it is possible to get an idea of the 

 shape, though not, perhaps, of the size, of the perfect valve. Like 

 the scutum, it consists of a 'chief plate' and a 'flange,' which, 

 however, lie nearly in the same plane. 



The ' chief plate ' is long, narrow, and symmetrical, about a median 

 line ; one end is broken across, the other is a blunt point. The two 

 lateral margins are symmetrically curved, nearly parallel at the 

 fractured extremity, but gradually approximate in the opposite 

 direction, so as to form feebly convex margins. The plate is marked 

 by nearly transverse growth-lines, which in the proximal moiety 

 are slightly distorted by a linear depression cutting across them 

 nearer one margin than the other. This depression traverses about 

 one-half the length of the plate, at first parallel to the margin, but 

 later bending away from it towards the middle line. 



On one side of the main plate is a thinner, narrow flange, triangular 

 in general form ; it is in reality mei'ely the slightly inflexed margin 

 of the valve, and, as in other cases, the lines of growth take a different 

 direction from those on the main plate, passing obliquely upwards 

 to cut the distal side of the triangle, which is uninjured, and slightly 

 thickened. 



mm. 



Length of fragment ... ... 70 



Breadth of main plate ... 22 



Greatest breadth over all 30 



Thickness 1-5 



Bemarlcs. 



Having given an account of these valves, I will proceed to 

 consider those characters which may enable us to place the fossil 

 in its proper genus. The question naturally arises, is the fossil 

 a member of the genus Scalpellum, or is it Pollicipes ? 



In his classic monograph on the fossil Cirripedes, Darwin ^ 

 points out the difficulties of deciding the matter when only a few 

 valves are available ; and in his work on the living forms, ^ he also 



1 " A Monograph on the Fossil Lepadidsc " : Palseont. Soc, 1851. 



2 "A Monograph on the sub-class Cirripedia (Lepadidas) " : Ray Soc, ISol. 



