402 R. BuUen Neidon — Egyptian Cretaceous Shells. 



teeth, wbich amount to about 65. These teeth have depressed 

 summits, hook-shaped ends, and are longest on the anterior side, 

 besides being of almost vertical disposition at the umbo. In these 

 details it diifers from Cucullcea tumida of D'Arohiac, a shell which in 

 some other characters appears to show certain resemblances, though 

 of less size and less inflated. It is of interest to mention that 

 C. tumida has already been recorded from the Senonian rocks of 

 Egypt by Professor Mayer-Eymar.' 



Remarks. — The specimen is contained in the same fawn-coloured 

 sandstone as Protocardia biseriata and a valve of Ostrea Villei. 

 Conrad's genus Trigonoarca is essentially Cretaceous, and from the 

 peculiar chai'acter of its teeth appears to be related to Cucullcea, 

 Axinea, and Noetia. 



Horizon. — Turonian. 



Distribution.—" Sheet 33 " : Coll. Geol. Surv. Egypt (No. 1,044, 

 Box No. 56c). 



Genus ARCTICA, Schumacher, 1817. 



Nouv. Syst. Hab. Test., 1817, p. 145. 



Type. — Venus Islandica, Linnasus [syn. Cyprina, Lamarck, non 

 Linnaeus]. 



Arctica Barroisi, Coquand. PI. XVI, Fig. 5. 



Cyprina Barroisi, Coquand, " Etudes Suppl. Pal. Algerienne " : Bull. 

 Ac. Hippone (Bone), No. 15 (1880), p. il3 (not figured). 

 Peron : " Desc. Moll. Foss. Cretaces Tunisie," pt. ii 

 (1891), p. 298, pi. xxix, figs. 8, 9. 



Description. — Shell triangular, thick, very convex, higher than 

 wide, marked by concentric striations, insequilateral ; anterior side 

 short, excavated beneath the umbones ; posterior region long, narrow, 

 rounded at margin ; umbones prominent, incurved ; muscular scars 

 prominent. 



Coquand's original diagnosis of this species as here given was 

 founded upon spechuens obtained from the so-called Santonian 

 beds of Algeria, but without being represented by figures. The 

 excellent illustrations, however, given by M. Peron, of the same 

 shell from Tunis, help to supply this omission in the history 

 of the species. It is evidently chiefly found as a cast, for 

 the excavation beneath the beaks is very apparent, not only in 

 Peron's figures, but also in actual specimens from Tunis preserved 

 in the British Museum. Furthermore, neither Coquand nor Peron 

 refer to internal characters, but one of the present Egyptian specimens 

 exhibits a great width of hinge-area and shows the lower of the two 

 anterior teeth ; and, although somewhat obscure in details, the hinge- 

 area may be said to resemble what is present in such forms as 

 Arctica rostrata (Sowerby), etc. 



The species is related to Cyprina cordiformis of D'Orbigny, 

 a European Albian shell, which, however, has prominent radial 

 striaa in addition to concentric ornamentation on its valves, besides 



1 " Zur Geologie Egyptens" : Yiert. A^at. Ges. Zurich, vol. xxxi (1886), p. 246. 



