• 



[U'i MR. G. S. BRADY'S MONOGRAPH OF 



concave. Valves marked with several (8-10, Sars) more or less longitudinal acute ele- 

 vated ribs, one or more of which terminate behind in sharp spinous points. Colour 

 variable — yellowish, brown, or slaty blue. 

 I. tigth ,'„ in. 



Ihrh. Off Holy Island (Northumberland), Birterbuy and Gahvay Bays, and in shell-sand from South 

 Wales (G. 8. B.\ j Cumbrae and Shetland (Mr. D. Robertson) ; Loch Fyne, and in rock-pools, 

 Arraiij N.B., and Herm (Rev. A. M. Norman); Aberdeenshire coast (Mr. Dawson); Isle of Skye, 

 Plymouth, Isle of Portland (Rev. G. Barlee). 



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This appears to be the commonest and most widely distributed of the deep-water 

 species of Cytherura, often occurring in considerable numbers. It exhibits much varia- 

 tion in the number and direction of the ribs with which the surface of the shell is 

 marked ; and I have met with one specimen, apparently referable to the same species, in 



hich the ribs were quite obsolete except on the ventral surface. This specimen is 



■ 



represented (figs. 9-11), and was taken in Birterbuy Bay, Connemar 



1."). Cytherura claturata, G. 0. Sars. (Plate XXIX. figs. 43-46.) 



Cytherura clathrata, G. O. Sars, he. cit. p. 77. 



Scandinavian type? Distribution: Recent— Norway, Great Britain, Ireland. Fossil— Glacial and 



rai 1 1 beaches, Scotlaud and Norway. 



Carapace of the female, as seen from the side, subtriangular, greatest height in the 

 middle, and equal to nearly two-thirds of the length ; anterior margin narrow, rounded, 

 and bearing four or five short broad teeth; posterior margin produced into an obtuse 

 laminar process; superior margin strongly arched in the middle, inferior convex. Out- 

 line, as seen from above, subovate, widest in the middle, extremities obtusely mucronate; 

 ureatest width about equal to half the length. The shell surrounded in the greatest 

 part of its circumference by a laminar belt or keel. " The male lower and less strongly 

 arched above " (Sars). The right valve is much larger than the left. Shell marked 

 with irregularly reticulated ribs ; mostly one conspicuous ridge running longitudinally 

 near the middle of the valves, and one or two, which are rather less distinct, branching 

 obliquely from it. Colour brown. 



Leneth A in. 



&"" 5-2 



(Mr. D. 0. Brown) ; Orraeshead and Oban (M- 



Ctth krura cellulosa (Norman). (Plate XXIX. figs. 47-50, 60.) 





Durham 



Nor 



17-20, and pi. vi. fig. 17. 

 Cytherura nana, G. O. Sars, loc. cit. p. 78. 



British type. Distribution : Recent-Korwiiy, Great Britain, Ireland. Fossil 



Scotland. 



Valves, as seen from the side, nearly semicircular, except that the infero-posteal angle 

 w broadly and obliquely truncate; greatest height in the middle, and equal to nearly 

 two-thirds of the length; narrow and obliquely rounded in front; produced behind, 

 above the middle, into a short obtuse process. Superior mar-in very boldly arched, 





