CYTHERE. 151 



margin. The posterior beak of the right valve is more squamous and often two or three 

 times emarginate. Surface of the shell covered with closely-set circular impressed puncta. 

 The male does not differ much in shape from ih.Q female. 

 Length, ^th of an inch. 



Cytliere convexa is in the living state widely distributed round the British coast, but 

 nowhere occurs very abundantly ; it ranges from the littoral zone to depths of about 

 thirty fathoms, but does not appear to have been noticed either in the seas or glacial 

 deposits of Scandinavia. 



Some of the forms described and figured by Professor T. Rupert Jones under the name 

 Cythere punctata are undoubtedly referable to the present species, but some of the synonyms 

 and references given by that author do not appear to us to be applicable. We are not 

 acquainted with the figures of C. punctata given by Roemer, but that of Reuss, if meant 

 for the present species, is certainly very bad, while his Cypridina punctatella, which is 

 doubtfully referred by Professor Jones to the young of the present species, evidently 

 belongs to the group assigned in this memoir to the genus Loxoconcha. The same may also- 

 be said of Bosquet's Cytliere punctatella. Lastly, it may be noted that G. O. Sars has 

 erroneously applied Dr. Baird's name {convexa), having assigned it to a totally different 

 form, the Cytheropteron latissimum of this Monograph. 



Distribution. Recent. — Great Britain and Ireland, Levant, Bay of Biscay. 



Fossil. — Scotland : Raised beaches, Cumbrae and Oban ; West Tarbert Silt. Ireland : 

 Portrush ; New Docks, Belfast. 



14. Cythere cicatricosa, Beuss. Plate XIV, figs. 7 — 10. 



1849. Cypridina cicATKicosA, iJewss. Die fossil. Entomostrac. Oesterreich. Tertiar- 



beckens, p. 27, pi. ix, figs. 21 a, b. 



1852. Cythere cicatricosa, Bosquet. Entom. foss. terr. tertiair. France, p. l?t, 



pi. iii, fig. 13. 



1865. — ARBORESCENS, Brady. Ann. Mag. N. H., vol. xvi, pi. ix, figs. 5 — 8. 



Carapace, as seen from the side, subovate, highest in the middle, greatest height equal 

 to two thirds of the length ; anterior extremity broadly rounded, posterior slightly 

 produced below the middle ; superior margin boldly arched, inferior somewhat convex and 

 slightly sinuated in front of the middle. Seen from above, ovate, tapering evenly to the 

 extremities, which are sharply pointed ; greatest width in the middle and equal to half 

 the length. The end view is somewhat pyramidal, being pointed at the top and widest 

 below the middle ; the base broad and rounded. Shell-surface marked with closely set 

 rounded or subangular impressions, which on the ventral aspect coalesce so as to form 

 beaded furrows. 



Length, g-gth of an inch. 



