from Sinai and Egypt. 



225 



Subclass IRREGULARIA. 



Order 1. GNATHOSTOMATA. 



Suborder HOLECTYPINA. 



Family PYGASTERID.E. 



HOLECTYPUS. 

 1. HoLECTSPUS CENOMANENSis, Guerangor, 1859. 



Holedypus cenomancnsis, Gueranger, in Cotteau & Triger : E'ch. Dep. Sarthe 



(1859), p. 173, pi. XXX, figs. 5-10. 

 Holectypus cenomanensis, Duncan, 1<S65 : Ech. Coast Arabia, Quart. Journ. Geol. 



Soc, vol. xxi, p. 354. 

 Holectypus cenomanensis, Fourtau, 1899: Rev. E'ch. foss. E'gypte, Mem. Inst. 



E'gypt., vol. iii, fasc. 8, p. 625. 



Distribution. — Cenomanian : Algeria, France, etc. ; Jebel um 

 Eaiyig, north-eastern Sinai. L 3483. Collected by Dr. W. F. 

 Hume. Cretaceous Marls : Jebel el Araba, Wadi el Araba, Sinai. 

 L 4220. Collected by the late T. Barron, Esq. 



Dimensions : 



L4220. 



Diameter 

 Length ... 



Width 



Height 



Length to width . . . 

 Length to height... 



L 3483. 



40"5mm. 

 39 mm. 

 21 mm. 

 100 : 96-3 

 100: 51-8 



22-5 mm. 

 22-25 mm. 

 10 mm. 



Affinities. — The characteristics of this species are its comparatively 

 large size (up to 45 mm. in diam.), the subpentagonal or subcircular 

 form, the very low, conical form, and the great size of the periproct, 

 which is acuminate at both ends, and extends from the peristome to 

 the margin. 



It differs from the Echinoconus egyptiacus, d'Orb./ by its low 

 height ; from H. excisus, Cott.,^ by the fact that the periproct does 

 not notch the posterior margin of the test. M. serialis, Deshayes,* 

 is much smaller, and has less numerous tubercles on the inter- 

 ambulacral plates; and so also has JH. jullieni, P. & G.* The latter 

 is a Turonian and Senonian species, and in spite of its somewhat 

 lower height is a near ally of JJ cenomanensis. 



2. Holectypus turonensis (Desor), 1847. 



In Agassiz & Desor: Cat. rais., Ann. Sci. nat., ser. in, vol. vii, p. 146. 

 Cotteau: Pal. franc;., Terr, cret., vol. vii (1861), p. 56, pi. 1018. 

 Cotteau, Peron, & Gauthier: E'ch. foss. Alger., fasc. 6 (1879), p. 87. 



1 Cotteau, Peron, & Gauthier: E'ch. foss. Alger., fasc. 5 (1879), p. 172. 



2 D'Orbigny: Pal. franc;., Terr, cret., vol. vi, p. 544, pi. 1005, figs. 7-9. 



' See e.g. the figure in Cotteau & Triger: E'ch. Dep. Sarthe, p. 368, pi. Ixii, 

 figs. 1, 3. 



* See Desor : Sjti. E'ch. foss., p. 174, pi. xxiii, figs. 6-9. 



* Peron & Gauthier: E'ch. foss. Alger., fasc. 6 (1880), p. 85, pi. vi, figs. 3-7; 

 fasc. 7 (1881), p. 91. 



DECADE T. — VOL. HI. — NO. V, 



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