272 MOLLUSCA FROM THE CRAG. 



"Animal oblong, mantle closed in front, except a plain-edged orifice for the 

 passage of a lanceolate foot; siphons short, united, unequal, the branchial largest, 

 both bearing a few long filiform cirrhi at their sides, extending beyond the orifices ; 

 anal siphon with a very extensile membranous valve." Forbes and Hanley. 



1. NE^RA JUGOSA, S. Wood. Tab. XXX, fig. 7, a, 6. 



CORBULA ? SULCATA. S. Wood. Catalogue, 1840. 



Spec. Char. Testa parvd, transversd, incequilaterali, aquivalvi ? compressd, juyosd ; 

 antice rotundatd; postice subrostratd, et angulatd ; cardine unidentato. 



Shell small, transverse, inequilateral, equivalved ? compressed, ridged ; anterior side 

 rounded \ posterior somewhat beaked, and angulated ; hinge with one tooth. 



Length, ^ inch. Height, T J T inch. 



Locality. Cor. Crag, Sutton. 



This shell is not rare in the Coralline Crag, but as yet I have met with it only in 

 one locality, and never with the valves united. 



It much resembles the figure of one of the species from the Paris Basin, Corbula 

 striaretta, Desh., Coq. Foss. des Env. de Par., torn, i, p. 54, pi. 8, figs. 12 15, but 

 differs in being less than half the size, as well as in other characters ; and I believe it 

 to be distinct, depending as I am obliged to do upon the figure and description above 

 referred to. 



In our species the hinge of the right valve has one obtuse and somewhat oblique 

 tooth on the anterior side of the *umbo, with a depression between it and the dorsal 

 edge, into which fits an elevated portion of the margin of the left valve, while on the 

 siphonal side of this (left valve) is an elongated and elevated projection that interlocks 

 within the dorsal edge of the right valve ; between these, and immediately beneath 

 the umbo, is an oblique pit, where the ligament was situated, and entirely 

 within the shell ; so much so that I doubt whether any part of it could have been 

 seen in the living animal when the valves were closed. The dorsal margin 

 slopes at an angle of about 45, and a truncated beak is formed by the siphons ; 

 the upper part being somewhat elevated producing an obtuse keel from the umbo upon 

 the slope on that side. The exterior has from eight to ten rounded ridges, with 

 depressions or sulci between them of about the same breadth ; but upon the younger 

 part of the shells these markings are obsolete, being smooth, or nearly so, about the 

 umbo. The shell is by no means thin, though the ridges are generally visible upon 

 the interior. The adductor-mark on the siphonal side is of a triangular form, and 

 deeply impressed, placed rather backward ; and the sinus- in the mantle-mark mode- 

 rately deep. 



The provisional name given to it in my ' Catalogue' is obliged to be changed, in 

 consequence of its having been used by Dr. Lovn for a very different species. 



