48 Frederick Chcqrnian : 



entire valve margin. Alar beak moderately salient, gradually 

 rising from the antero-dorsal angle towards the postero-ventral, 

 and terminating in a sharp marginal angle; surface of ala depressed 

 under the carinal edge, near the posterior extremity of the shell ; 

 caudate portion of the carapace much compressed. Edge view 

 suboval. compressed at the extremities, and broader towards the 

 posterior third. Shell surface covered with a fine network of 

 irregularly polygonal areolae. 



Dimensions. — Length, .58 mm.; height, .31 mm.; thickness of 

 carapace. .16 mm. 



Affinities. — So far as T am aware the nearest living species is 

 C. ivellingtoniense , G. S. Brady. i which was dredged in Wellington 

 Harbour. New Zealand. C. reticosutn differs in having more quad- 

 rate valves, more prolonged alae and a reticulated ornament. In 

 general form it is like u much compressed variety of Ci/theropteron 

 hatesfordiense. 



Occurrence. — Bore 10. 195-225 feet (Kalimnan). 



Cytheropteron rostratu.m, sp. nov. (Plate IX., Figs. 4Ia, 6). 



i 



De-^cription. — Sliell compressed, ovate; in side view arcuately 

 oval, highest in the middle ; anterior extremity compressed, nar- 

 rowly loundc'd. tlic iKisterior extremity subacute, excavated ven- 

 ti-ally ; dorsal margin strongly arched, curving steeeply to the 

 extremities. Ventral margin concave in tiie lower middle, and 

 convex towards the aiiTfrior end. Edge view compressed ovate, 

 arute at anterior. l)luiit at posterior end. Surface of valves finely 

 and striately punctate, tlie ornament being concentric with the 

 margins. The surface markings are more distinctly seen when the 

 shell surface is moistene<l. 



Dimensions. — Length. A2'-] nnii. ; height. .21 nun. ; thickness of 

 carapace. .21 mm. 



Affinities. — Tlie neaiX'sT allied s])C'L'ics to the above is Ci/there 

 scaphoides, CI. S. Brady .2 from KcMgnelen Island, in 20-511 fathoms. 

 They diffei-, liowever. in the outline, for the living species is oblong 

 and not arcuate. The sui-fare ornament in ])ot]i forms is similar. 



Occurrence. — Bore 11. 2(17-270 feet (Janjukian). 



1. Rep. Ch.-ill. Zool., vol. i., i-t. iii., 1880, p. 13(>, pi. xxxiv., fi;;s. 4«-(/. 

 •2. ToTi). s\ipra cit., p. VMi. pi. wxiii., fiys. !«-(/. 



