CYTHEROPTERON CUSPIDATUM. 37 



Length "92 ; height '6 ; thickness '8 mm. 



Carapace subrhomboidal in side view ; broad, smooth, and convex, but sloping 

 to the front and back ; highest (widest) at the anterior third, and thickest behind 

 the middle ; bluntly sagittate and with sharp barbs in edge view ; front rounded 

 with a short prominent curve, which slopes off both above and below ; back 

 elliptically arched ; ventral margin nearly straight, but overhung by the long, 

 broad, angular wing, pointing downwards and backwards ; hinder margin do- 

 pressed, narrow, and truncate with sharp angles. 



This is different from Gytheropteron pipistrella, Brady (' Trans. Zool. Soc.,' 

 vol. X, 1878, p. 404, pi. Ixix, figs. 2 a — d), in the outline of the valve, and the 

 shape and backward position of the wing. 



Locality. — Chalk, near the Gobbins, co. Antrim. 



5. Gytheropteron ? phyllopterum (Bosquet). Plate III, figs. 9, 10. 



Cttheee phtlloptera, Bosquet. Mem. Coram. Carte geol. Neerlande, vol. ii, 



1875, p. 116, pi. vii, figs. 10 a— d. 

 — (Cttheeeis) spiculata, Jones, MS. Syst. Lists, &c., Belfast Nat. Field 



Club, vol. i, Appendix iii, 1875, 

 pp. 81, 92. 



Length "825; height "45; thickness (with spines) "75 mm. 



Mr. Wright's specimens from the Island of Magee, co. Antrim, and Keady Hill, 

 Derry, nearly agree with M. Bosquet's species above quoted, for some have a 

 smoother front margin and a more spinose projection on each valve than shown 

 in our figs. 9 and 10. The position of the great spine varies somewhat, being more 

 forward in some cases than in others, as shown by the figures ; it is nearly mid- 

 ventral in our fig. 9 and Bosquet's figs. 10 b and c, but further back in our fig. 

 10 and Bosquet's fig. 10 a. The similarity of these to Cythereis cerato-ptera 

 renders our determination uncertain. 



Localities. — Chalh, Ballytober, Island Magee, co. Antrim, and Keady Hill, co. 

 Londonderry. 



Foreign. — Chalk, St. Pierre (Limbourg), and Ciply, near Mons. 



6. Gytheropteron cuspidatum, sp. nov. Plate III, figs. 4 and 5. 



Length '65 ; height -3 ; thickness (with spines) "7 mm. 



Long, low (narrow), subtriangular ; straight on the dorsal, obliquely arched on 

 the ventral border ; rounded and denticulate on the front margin, but prominent at 

 the antero-dorsal angle; contracted and subacute behind (broken in fig. 4). The 



