CYPRINA. 



117 



margin truncated, 



hi"'li. 



Postcro-dorsal region flattened. Umbones pi-oniinent, 



anterior, curved inwards, 

 concentric striae. 

 Measurements : 



Lunnlar region excavated. 



Ornamentation consists of 



(«) 



10 



(9) 



20 

 15 



(10) 



45 



38 



(11) 



58 mm. 

 52 „ 



Affinities. — In G. ligeriensit^, d'Orbiguy,^ the umbones are less auterioi- in [nm- 

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

 G. (jnadrata. 



G. retjularis, d'Orbigny,- is distinguished from C. qudtlralti by its k>ss ine(jui- 

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

 smaller truncation of the posterior end. 



G. crassLcornis (Agassiz)'^ possesses a relatively higlier and less inequihiteral 

 sliell, witk moi'e prominent umbones, which are not so nuicli curved anterioi'Iy 

 as in G. quadrata. 



Ri'marlis. — The specimens from the Gault liave the shell more or less i)erfect]y 

 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 Ceuomaniau of Villers (Calvados), Rouen, St. Calais (Sarthe), 

 etc. 



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

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

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

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



1 ' Pal. Fran?. Terr, Cret.,' vol. iii (18-14), p. 103, pi. ccl.\xv, fi},'s. 1, 2 (not 3, 4). 



- Ibid., p. 100, pi. cel.x.xii, figs. 3—0 ; Tictet and Campiche, ' Foss. Terr. Cret. Sle. Croi.x ' (1805), 

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



3 ' Etudes crit. Moll. Foss., Myes' (1842), p. 30, pi. viii/, figs. 5—10 ; Pictet and CauipicLe, * Terr. 

 Crct. Ste. Croi.\' (' Matrr. Pal. Suisse,' scr. 4, 180.5), p. 220, pi. cxv, figs. 0—8. 



