from Sinai and Bgypt. 223 



2. Thylkchinus trigeanulatus, n.sp. (PI. XI, Figs. 9a-d!.) 



Test low and small ; circular ; it is flat below, is tumid at the 

 ambitus, and somewhat pointed above. Apical area small. Peristome 

 decagonal, with broad buccal slits. 



Ambulacra, about 11 compound and 5 abactinal primary plates, in 

 a vertical series. The uppermost, or the two uppermost, compound 

 plates are smooth, and have only a low granule. Each ambital 

 plate has a single prominent tubercle, but little smaller than those 

 of the interambulacra. The boss occupies nearly the whole of the 

 non-poriferous part of the plate, and is surrounded by a thin single 

 row of small granules on its border. 



Interambulacra. — There are about 11 plates in each vertical series. 

 The plates are long and low ; the abactinal side is slightly concave. 

 The base of the tubercle is surrounded by a circle of low granules, 

 so that the scrobicular areas are non-confluent. Each plate typically 

 has three prominent granules, one in each of the two adambulacral 

 corners and one on the abactinal interradial corner. 



Dimensions : 



Diameter 22mm. 



Height 9 mm. 



Diameter of apical area 5-6 mm. 



Diameter of peristome ... ... ... ... ... 8-9 mm. 



Width, of ambiilacrum at ambitus ... ... ... 5 mm. 



"Width of interambulacrum at ambitus 8 '5 mm. 



Figures. — PL XI, Fig. 9a, test from below, nat. size ; Fig. 96, 

 from the side, nat. size ; 9c, upper part of an ambulacrum showing 

 the structure of the plates, by 4 diam. ; dd, part of an interambulacrum 

 at the ambitus, by 4 diam. 



Distribution. — Cenomanian — Cretaceous Marls : head of Wadi 

 Ethal, Sinai. L 3872. Collected by the late T. Barron, Esq., 1899. 



This ThylecMnus is represented by one specimen ; it is somewhat 

 distorted, but the characters are well shown. The ornamentation 

 reminds me most of Cyphosoma baylei, Cott. (Pal. frang., Terr, cret., 

 vol. vii (1864), pi. 1138, fig. 12), which, however, is a true 

 Cyphosoma. 



COPTOSOMA, Desor, 1858. 

 1. CoPTOsoMA ABBATEi (Gauthier), 1899. 



Cyphosoma abbatei, Gauthier, in Fourtau, 1899 : Eev. E'ch. foss. E'gj'pte, Mem. 



Inst. E'gj-pt., vol. iii, fasc. 8, p. 620, pi. i, figs. 2-6. 

 Cyphosoma abbatei, Fourtau, 1900: Notes E'ch. foss. E'gypte, p. 21. 

 Cyphosoma abbatei, Dacque, 1903 : Mitth. Kreidecomplex Abu Roash, Palseontogr., 



vol. XXX, p. 357. 

 Pseudodiadema, sp.,"Walther, 1887 : Apparition craie, BuU. Inst. E'gypt., 1887, p. 7. 



This species, well described by Gauthier, i^ represented by a good 

 series of specimens. They show that the ambulacra are not 

 diplopodous abactinally, so the species is a Coptosoma. 



Distribution. — Cenomanian or Turonian : eastern end of the 

 village of Abu Koash. 1 3792. Collected by H. J. L. Beadnell, Esq. 



