410 



MR. G. S. BRADY'S MONOGRAPH OF 



nearly parallel, anterior extremity obtuse, the posterior broadly mucronate. Surface of 

 the shell uneven, vaguely marked with ill-defined pits and furrows. 



Length in. 

 Hab. Shetland [Rev. A. M. Norman). 



Mr. Norman's collection contains one specimen only of this species. It is nearly allied 

 to Cythereis emarginata, Sars, but is very much larger, and has not the sharply defined 

 reticulated sculpture of that species ; the outline is also more irregular. 



19. Cythere finmarchica, Sars. (Plate XXXI. figs. 9-13.) 



Cythereis Finmarchica, Sars^ loc. cit. p. 41. 



Scandinavian type. Distribution : Recent — Norway, Great Britain, Ireland, Bay of Biscay, Cape 

 Verd. Fossil — Glacial, Scotland. 



Valves, as seen from the side, oblong quadrangular, rather higher in front than 

 behind ; length equal to twice the height. The anterior border is obliquely rounded and 

 angulated at its junction with the dorsum, often slightly toothed below. Posterior 

 extremity flattened and narrow, produced below, where it is divided into about four 

 broad, blunt teeth. Inferior margin straight or slightly incurved. Dorsal margin very 

 slightly arched, or sloping almost in a straight line from before backwards. Seen from 

 below, the outline is oval, with obtuse extremities and parallel sides, which are some- 

 times rather deeply sulcate in the middle. End view subtriangular, broad, and rounded 

 below, tapering above. The surface is marked with numerous rather large, shallow pits, 

 and is often transversely sulcate ; in front of the median sulcus is a large rounded 

 tubercle bearing the lucid spots, which are nine to twelve in number, and irregular in 

 arrangement (figs. 9, 13). Animal unknown. 



Length -^g in., height in. , V x ,5 

 Hab. Dredged off Oban {Mr. D. Robertson) ; Roundstone, in shell-sand (Dr. Alcock) ; Galway Bay, in 



shell-sand {Prof. Rowney) ; The Minch and Channel Islands, 15-30 fathoms {Mr. J. G. Jeffreys) ; 



Northumberland coast, 46 fathoms {G. S. B.) ; Devonshire coast {Mr. C. Spence Bate) ; in tide-pools, 



Herm {Rev. A. M. Norman). 



I at one time supposed this species to represent merely a stage of growth or a local 

 variety of C. tuherculata ; but this opinion I now believe to be untenable. The elongated 

 form of the valves (without tumidity behind), the posterior crenulation, and the one 

 central tubercle are constant characters. It will be seen, by reference to Plate XXX., 

 that the young forms of C. tuherculata always exhibit one central and two posterior 

 tubercles ; and the teeth of the posterior margin, when they exist at all, are really out- 

 growths of the shell, and not mere indentations of the bordering lamina as in the present 

 species. Moreover the anterior border of well-grown specimens of C. tuherculata is 

 almost sure to be fringed with spines, but in C. finmarchica is either entire or, at most, 

 slightly crenated, as shown in fig. 9. 



