CYTHERE. 163 



sharply cut sulcus. Shell-surface bearing a few distant, short, rigid hairs, and 

 ornamented with large, deep, angular excavations, mostly arranged in irregularly waved or 

 radiating lines ; there is usually a conspicuous rounded tubercle a little below and in 

 front of the centre of the valve, and two broad, rounded, and elevated ridges, one 

 running parallel with the ventral, the other with the dorsal margin, on the posterior half 

 of the valve; these are confluent behind, ending abruptly and thus forming a well- 

 marked transverse ridge or declivity; there is also a narrow elevated ridge running 

 parallel to and within the anterior margin. 

 Length, -^J^th of an inch. 



This species, like C. concinna, varies much in the amount of sculpture visible on its 

 valves, some specimens, as shown in fig. 17, being poorly marked, while others, of 

 which fig, 21 is a fair example, are very highly ornamented. In the British seas, at the 

 present day, it seems to be of rare occurrence, and confined to the northern and western 

 shores of Scotland, where it lives in considerable depths of water. It has been found 

 also by G. O. Sars on the coast of Norway. 



Distribution. Recent. — Baffin's Bay, Norway, Great Britain, Davis's Straits. 



Fotssil. — England: Bridlington. Scotland: nearly all the clay beds of the Clyde 

 district ; Raised beach, Oban ; Drip Bridge. Ireland : Portrush. Norway. 



30. Cythere latimarginata, Speyer. Plate XVI, fig. 6. 



1863. Cythere latimaeginata, Speyer. Die Ostrac. der Casseler Tertiarbild., p. 22, 



pi. iii, figs. 3 a — d. 

 1865. — ABYSSICOLA, G. O. Sars. Overs. Norg. mar. Ostrac., p. 43. 



Shell of the female, as seen from the side, elongated, subquadrangular, much higher 

 in front than behind, greatest height not more than half the length ; anterior extremity 

 obliquely rounded ; posterior truncate ; superior margin very prominent and angulated 

 above the eyes, slightly concave in the middle, then convex, and steeply sloping towards 

 the hinder end ; inferior distinctly sinuated in the middle. Seen from above, of 

 irregular form, showing on each lateral margin two subangular protuberances separated by 

 a deep furrow, both extremities being a little produced and truncate. Valves very hard 

 in structure, indistinctly areolated in the middle, surrounded by a wide and much 

 thickened margin, which forms two lips, the innermost of which is at each extremity 

 minutely dentate, and especially towards the posterior extremity is beset with rather long 

 hairs. Hinge-teeth of the left valve obsolete. 

 Length, ^th of an inch. 



One valve only of this species has come under our notice, from Hopton Chff, near 

 Yarmouth, and, this being imperfect we have had recourse for our description to the 



