414 



MR. G. S. BRADY'S MONOGRAPH OF 



outline, as seen from above, is oblong ovate or hastate, the junction of tbe hinge-margins 

 marked behind the middle by a deep, sharply defined sulcus. Ventral surface sulcate 

 along the whole length of the contact-margins, which are bordered by a broad, well- 

 defined, smooth band. End view ovate. The surface of the shell is marked with oblong 

 punctures, which are arranged chiefly in longitudinal rows, but in curved lines round the 

 anterior border. The valves, in typical specimens, are swollen behind, forming an abrupt 

 angular elevation, from which a longitudinal rib runs directly forwards, and two others 

 in an oblique direction towards the upper and lower margins of the valve ; the left valve 

 is considerably smaller than the right. Animal unknown. 

 Length in. 



Hab. In deep water^ rare. Coasts of Northumberland and Durham, 25-46 fathoms (G. S. B.); Ormeshead 

 and Oban {Mr. D. Robertson) ; Shetland {Rev. A. M. Norman) ; Hebrides and the Minch {Mr. J. G. 

 Jeffreys) . 



The specimen represented in figs. 19-22 is the form originally described by Dr. Baird 

 under the specific name quadridentata ; that shown in fig. 25 is a very similar form, 

 while fig. 23 differs only in being less angular and the surface-markings fainter. The 

 specimens from which figs. 26-30 were drawn appear to be merely a variety, or perhaps 

 the adult or the female of the same species. The peculiar characters of the ventral and 

 dorsal surfaces, as well as the elongated punctation, are distinctly retained. The spbcies 

 is a rare one, and I have had no opportunity of thoroughly examining the animal. 



26. Cytheue emaciata, Brady. (Plate XXXI. figs. 31-37.) 



Cy there emaciata, Brady, Brit. Assoc. Report, 1866, p. 210. 



Atlantic type. Distribution : Recent — Great Britain and Ireland. Fossil — Raised beaches, Scotland. 



Carapace, as seen from the side, compressed, quadrangular, higher in front than 

 behind; lengtb equal to more than twice the height. Anterior extremity flattened or 

 but slightly rounded, often fringed with a row of eight or nine teeth. Posterior extremity 

 narrowed, excavated above, produced and toothed below. Dorsal and ventral margins 

 nearly straight. Outline, as seen from above, oblong, widest behind, nearly thrice as 

 long as broad ; the ventral keel produced behind into two broad fimbriated processes. 

 The contact-margins on the ventral surface are bordered by two flattened ridges, forming 

 a very broad keel, which projects considerably behind. End view oval, with rounded 

 lateral protuberances. Surface marked with large pits arranged longitudinally ; in small 

 or young specimens the punctures are oblong, as in the preceding species; along the 

 middle of the valve runs a conspicuous elevated rib, a less distinct ridge within the 

 ventral margin, and another smaller one in an oblique direction behind the antero-dorsal 

 angle. Right valve larger than the left. Animal unknown. 



Length ^ to in., height -^o in- ^'-^ ^.5^ /.-J v 'K'^v^^ 



Hab. In deep water. Shetland {Rev. A. M. Norman) ; Peterhead and Ormeshead {Mr. D. Robertson) ; 



Hebrides {Mr. J. G. Jeffreys) ; Aberdeenshire coast {Mr. Dawson) ; Northumberland and Durham 



coasts, 35 fathoms, and Birterbuy Bay, 15 fathoms {G. S.B.); Devonshire coast, 60 fathoms {Mr. 



Spence Bate) ; in shell-sand from Roundstone (Dr. Alcock), Baltimore {Mr. E. C. Davison), and 



Galway Bay {Prof. Rowney) . 



$ 



