FEMALE. 245 



above the pit, and between it and the apex, there is a 

 transverse, oblong, deeper depression (b), within which, 

 the male is lodged. A small portion of the apex of the 

 valve projects over the terga. 



Terga, large, nearly equalling the scnta in area, flat and 

 sub-triangular ; the scutal margin is not quite straight. 

 The apex of the valve is thick and solid, and must have 

 projected freely for a length equalling one third of the 

 occludent margin. 



Carina, laterally broad, angularly bent ; slightly widen- 

 ing from the apex to the base ; internally, deeply concave. 

 The position of the umbo varies, in young specimens it is 

 seated at the uppermost point, and consequently in such 

 there is no upward growth ; in older specimens, from the 

 junction and upward production of that part on each side 

 of the valve, which I have called in fossil specimens the 

 intra-parietes, the valve is added to above the umbo, 

 but to a lesser degree than in S. vulgare. Slight ridges 

 separate the roof from the parietes, and the parietes from 

 the intra-parietes. 



Hostrum, minute, narrow, widening a little from the 

 apex downwards, inserted like a wedge between the 

 umbones of the rostral latera, and hardly projecting above 

 their upper margins, so as to be easily overlooked : 

 internally concave. 



Upper Latera (fig. 1 a), quadrant-shaped, with a deep 

 square notch cut out of the arched margin, which notch 

 receives the upper point of the carinal latera ; the surface of 

 the valve between the notch and the umbo is depressed.* 



Rostral Latera, small, gradually widening from the 

 umbo to the opposite end, which is obliquely rounded. 



Infra-median Latera, approaching to diamond-shaped, 

 placed obliquely to the longer axis of the capitulum ; or 

 the upper part may be described as spear-shaped. 



* The only valve which I have seen at ail like this, is a fossil specimen 

 from the Upper Chalk of Scania ; this is described in my memoir on the 

 Fossil Lepadidse (Palseontographical Society), under the name of Scalpellum 

 solidulum (Tab. 1, fig. 8, e,f), and is perhaps erroneously there considered 

 as a carinal latus. 



