CYTHERE. 155 



abruptly angular at each extremity, between which it is more or less concave ; inferior 

 slightly waved. Seen from above, the outline is broadly hastate or boat-shaped, widest 

 near the posterior extremity, tapering gently and in a curve towards the front, but 

 suddenly and steeply backwards ; margins irregularly sinuous ; greatest width about 

 equal to the height. End-view subtriangular, base broad and flat, apex obtusely 

 rounded, sides excavated. Shell-surface uneven, rugose, often obscurely reticulated, the 

 interstices being finely punctate ; a conspicuous polished and rounded tubercle over the 

 anterior and two near the posterior hinge ; a strongly marked longitudinal ridge 

 running along the whole length of the valves just within the ventral margin. 

 Length, ^th of an inch. 

 Distribution, decent. — Baffin's Bay, Norway, Great Britain. 

 Fossil. — Scotland : Duntroon, Kyles of Bute, Kilchattan, Cumbrae, Dumbarton^ 

 Cartsdyke, Inch Lonaig, Tangy Burn, Terally. Canada : Post-tertiary beds. 



20. Cythere globulifera, Brady. Plate IX, figs. 18 — 20, and (?) 21, 22; 



Plate XII, figs. 11, 12; and Plate XV, 

 figs. 19, 20. 



1868. Cythere GLOBrLiFEKA, Brady. Monog. Eec. Brit. Ostrac, p. 406, pi. xxxi, 



fig. 42. 



Valves, as seen from the side, subcuneiform or subquadrangular, greatest height in 

 front, and equal to nearly two thirds of the length. Anterior extremity broadly and 

 evenly rounded ; posterior narrower and obliquely rounded ; superior margin perfectly 

 straight and terminating in an obtuse angle at each extremity ; inferior straight or very 

 slightly sinuous. Outline, as seen from above, irregularly ovate, sinuous, widest at the 

 posterior third ; width equal to half the length ; surface delicately reticulated, and 

 towards the anterior and inferior margins concentrically rugose, bearing also, near the 

 superior margin, three large subglobular tubercles, and near the lower margin an 

 elongated alseform projection, which extends over a large portion of the ventral 

 surface. 



Length, ^th of an inch. 

 This species was first described by Mr. Brady from a single specimen found in shell- 

 sand by Dr. Alcock at Boundstone. The specimens found by us in the Scotch glacial 

 clays do not materially difier from the Roundstone specimen,, and serve to establish the 

 species on a more satisfactory basis than before. It is possible that the difierence of 

 outline between figs. 18 and 19 (Plate IX) may be sexual, the former representing the 

 male, the latter the female. The valve represented in figs. 21 and 22 is, perhaps, not 



