H. BuUen Neivton — Egyptian Cretaceous Shells. 401 



The above represents Conrad's original account of a Lebanon shell 

 which was regarded as Jiu'assic, but which later authorities have 

 more correctly recognized as Cretaceous (Turonian of Hamlin). 

 Certain specimens in the Egyptian Collection exhibit the sculpture of 

 this species. The broad, convex, concentric ribs are each separated 

 by a furrow of lesser width, whilst a series of radial cost^ ornament 

 the oblique posterior area. The concentric stri^ are finer, closer 

 together, and more numerous on the umbonal region than in a more 

 ventral direction. The species is closely related to Gardinm Hillanun 

 of Sowerby, from the Blackdown Beds of England, and seems to 

 differ chiefly in its coarser and more deeply sulcated concentric 

 ornamentation. 



Dimensions. 



Single valve— Height 45 mm. 



Length... ... ... ... ... 44 ,, 



Diameter ... ... ... ... 15 ,, 



Eemarks. — The valves occur in a fawn-coloured sandstone, and are 

 associated with Trigonoarca multidentata and one of the specimens of 

 Ostrea Villei. They are partially covered with matrix, so that the 

 posterior areas are not seen in all cases. 



Horizon. — Turonian. 



Distribution. — Bhamdun, Mount Lebanon, Syria; and "Sheet 33": 

 Coll. Geol. Surv. Egypt (No. 1,042, Box No. 54c ; No. 1,044, Box 

 No. 56c). 



Genus TRIGONOARCA, Conrad, 1867. 



American Journ. Conch., vol. iii (1867), p. 9. 



Journ. Ac. Nat. Sci. Philadelphia, ser. 2, vol. iv (1860), p. 281, 

 pi. xlvii, fig. 20. 



Type. — Cucullcea Maconensis, Conrad. 



Trigonoarca multidentata, sp. nov. PI. XVI, Fig. 4. 



Description. — Shell subtrigonal, arched, anterior margin rounded, 

 posterior area obtusely angulated and abruptly truncated ; cardinal 

 region nearly semicircular, composed of numerous, slightly flexuous, 

 radiately arranged, elongate, dejoreased denticles, which extend 

 down each side to the ventral margin of the adductor scars ; 

 scars large, posterior one longest and furnished with a projecting 

 marginal edge ; surface with more or less distant concentric growth- 

 lines, which are crossed in the ventral area by nearly obsolete 

 radial costse. 



Dimensions. 



Left valve— Height 75 mm. 



Length 79 ,, 



Diameter ... ... ... ... ... 25 ,, 



These characters have been drawn up from a single left valve 

 which represents the only specimen in the collection. Although 

 more or less of the nature of a cast, it is in a fair state of 

 preservation, and is distinguished from all other forms by the 

 regular formation and enormous number of the closely arranged 



DECADE IV. VOL. V. — NO. IX. 26 



