CYPRINA. 



147 



margin truncated, high, 

 anterior, carved inwards, 

 concentric strige. 



Measurements : 



Postero-dorsal region flattened. Umbones prominent, 



Ornamentation consists of 



Lunular region excavated. 





(i) 



(2) 



Length . 



54 



46 



Height . 



40 



41 



(7) 



(8) 



(9) 



(10) 



(ii) 



46 



40 



20 



45 



58 mm. 



39 



.> .> 



•JO 



15 



38 



52 „ 



(3) (4) (5) (G) 



37 35 26 23 



34 31 24 19 



(1 — 6) Gault, Folkestone. 



(7—9) Rye Hill Sand, Warminster. 



(10) Chloritic Marl, Maiden Bradley. 



(11) Base of Chalk, Chard. 



Affinities. — In 0. ligeriensis, d'Orbigny, 1 the umbones are less anterior in posi- 

 tion, and the angle between the posterior and the dorsal margins is larger than in 

 G. quadrata. 



G. regularis, d'Orbigny, 2 is distinguished from G. qnadrata by its less inequi- 

 lateral and more regularly globose shell, by its less incurved umbones, and the 

 smaller truncation of the posterior end. 



G. crassicomis (Agassiz) 3 possesses a relatively higher and less inequilateral 

 shell, with more prominent umbones, which are not so much curved anteriorly 

 as in G. quadrata. 



Remarks. — The specimens from the Gault have the shell more or less perfectly 

 preserved, but most of the examples from higher beds are, like the type, in the 

 form of internal casts. The specimens found in the Chalk Rock are rather 

 imperfect, but do not appear to differ specifically from those found at lower 

 horizons. 



Type. — The locality of the type is not given by d'Orbigny, but he records 

 specimens from the Cenomanian of Villers (Calvados), Rouen, St. Calais (Sarthe), 

 etc. 



Distribution. — Upper Gault of Folkestone. Upper Greensand (zone of Schlcen- 

 bachia rostrata) of Devizes {fide Jukes-Browne). Rye Hill Sand of Warminster. 

 Base of the Chalk of Chard. Chloritic Marl of Maiden Bradley and the Isle of 

 Wight. Chalk Rock of Morgan's Hill near Devizes, Cuckhamsley, and Luton. 



1 'Pal. Franc. Terr. Cret.,' vol. iii (184-4), p. 103, pi. eclxxv, figs. 1, 2 (not 3, 4). 



3 Ibid., p. 100, pi. eclxxii, figs. 3 — 6 ; Pictet and Campiche, ' Foss. Terr. Cret. Ste. Croix ' (1805), 

 p. 224, pi. cxv, figs. 1, 2. 



3 'Etudes crit. Moll. Foss., Myes' (1842), p. 36, pi. viii/, figs. 5—10 ; Pictet and Campiche, ' Terr. 

 Cret. Ste. Croix' ('Mater. Pal. Suisse,' ser. 4, 1865), p. 226, pi. cxv, figs. 6—8. 



