Vol. 59.] A LOWER-GREENS AND EOSSILIFEROUS BAND. 255 



of growth ; some specimens show a dark line on the smaller valve, 

 indicating the presence of a septum ; the front margin is sharp and 

 circular, showing no fold. 



Davidson remarks that he had seen the interior of a specimen 

 from the Tourtia of Belgium, which showed that it belonged to the 

 genus Magas. This species occurs in the Tourtia round Tournay, 

 where it is rare and not well preserved. It is not given in 

 Ton Decken's list of the species which occur in the Tourtia of 

 Essen (Westphalia). 



The Shenley specimens of Magas ort/iiformis show slight varia- 

 tions in the relative convexity of the valves, and in the thickening 

 of the front margin ; some attain a larger size than the shell 

 figured by Yicomte d'Archiac. 



Measurements of Magas orthiforihs (in millimetres). 



Length. Breadth. Thickness. Apical angle. 



A large specimen 12 : 50 12-00 7'5 108° 



Medium specimen 8'75 10-25 4"0 95° 



Small specimen 6*50 6'75 3'5 92° 



Terebrirostra lyra (Sowerby) var. inctjrvirostrttm, nobis. 

 (PI. XVIII, figs. 1 a-2 b.) 



1816. Lyra Meadi, Cumberland MS. 



1818. Terebratula lyra, J. Sowerby, ' Min. Conch.' vol. ii-, p. 87 & pi. cxxxviii, 



fig. 2. 

 1847. Terebrirostra lyra, A. d'Orbigny, ' Pal. Franc. Terr. Cret.' vol. iv, p. 129 



& pi. dxix, figs. 11-19. 

 1852. Terebrirostra lyra, Davidson, ' Brit. Cret. Bracliiop.' Monogr. Pal. Soc. p. 32 



& pi. iii, figs. 17-28. 

 1900. Terebrirostra lyra, Jukes-Browne, ' Gault & Upper Greensand of England ' 



[Cret. Rocks of Britain, vol. i] Mem. Geol. Surv. p. 66. 



This remarkable brachiopod has been often figured (see David- 

 son's ' British Cretaceous Brachiopoda ' for list of authors). 



Terebrirostra lyra, occurs in the Upper Greensand of Horn- 

 ingsham near Warminster, and in various localities in Somerset 

 and Dorset, and in the arenaceous Cenomanian of Devon. It is 

 a rare fossil in the Cenomanian at Cape La Heve, near Havre 

 (France). 



We have found several specimens of a variety of this species at 

 Shenley, but they are difficult to extract without breaking off the 

 long beak. Our specimens differ from those figured by Davidson in 

 having finer and more numerous ribs, also in having the long beak 

 more incurved ; but as they closely resemble the Havre T. lyra, 

 we think it advisable only to consider them as a variety, for which 

 we propose the name of in cur viro strum. 



Some of our shells have finer ribs than the Havre variety, and 

 are often more globose, but do not differ from it more than the 

 latter does from the Warminster specimens ; the Havre shells often 

 show the remarkable incurved beak. Mr. Jukes-Browne states (op. 

 supra cit. p. 66) that Terebrirostra lyra is rare, but characteristic of 

 the Warminster beds. 



