446 



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. 

 Length in. ,^-o'^ av>- 



Hab. OS Holy Island (Northumberland), Birterbuy and Galway Bays, and in shell-sand from South 

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

 Arran, N.B., and Herm [Rev. A. M. Norman) ; Aberdeenshu-e coast [Mr. Dawson); Isle of Skye, 

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



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

 species of Cytherurai 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 

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

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



15. Cytherura clathuata, G. O. Sars. (Plate XXIX. figs. 43-46.) 



Cytheruru clathrata, Gr. O. Sars, loc. cit. p. 77. 



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

 raised beaches, Scotland 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 ; 

 greatest 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. 



Length ^ in. . 



Hab. Dredged oflf Yarmouth [Mr. D. O. Brown) ; Ormeshead and Oban [Mr. D. Robertson). 



16. Cytherura cellulosa (Norman). (Plate XXIX. figs. 47-50, 60.) 



Cythere cellulosa, Norman, Nat. Hist. Trans. Northumberland and Durham, vol. i. p. 22, pi. v. figs. 



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

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



British type. Distribution : Recent — Norway, Great Britain, Ireland. Fossil — Glacial, Norway, 

 Scotland. 



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

 is 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 margin very boldly arched, 



