224 Prof. J. W. Gregory — Fossil Echinoidea 



2. CoPTOsoMA GUNNEHENSis,' n.sp. (PI. XI, Figs. \Oa-d.) 



Diagnosis. — Test of medium size ; subpentagonal in form. Flat 

 base; somewhat tapering below. The middle area of the inter- 

 ambulacra is depressed near the apical system. 



Apical system apparently somewhat small, pentagonal. 

 Peristome large, subdecagonal, with broad buccal slits. 

 Ambulacra: 13 compound plates each with one well -developed 

 tubercle. Scrobicular circles confluent ; a well -developed double 

 series of granules down the middle line of each area. Four con- 

 stituents in each ambital ambulacral plate. 



Interambulacra: 12-13 plates in each vertical series. At the 

 ambitus each plate bears two well-developed tubercles ; the plates 

 are bent into a step-like form, the central tubercles being half the 

 width of the plate nearer the actinal surface. 



Granulation scanty ; the two scrobicular areas of each plate are 

 confluent, but they are not confluent with those of the plates above 

 and below it ; usually two granules on the side of the plate near the 

 ambulacrum. 

 Dimensions : 



Diameter 27 mm. 



Height 8 mm. 



Diameter of apical area 9-l3mm. 



Diameter of peristome .. . ... ... ... ... 13mm. 



"Width of ambulacrum at ambitus ... ... ... 5*5 mm. 



Width of iuterambulaorum at ambitus 11mm. 



Distribution. — Cenomanian (?) : Jebel Gunneh, Sinai. L 3506. 

 Collected by Dr. W. F. Hume. 



Figures. — PL XI, Fig. 10a, type-specimen from above, and 

 Fig. 10b, from the side, nat. size ; Fig. 10c, a compound ambital 

 ambulacral plate, by 4 diam. ; Fig. lOd, ambital interambulacral 

 plates, by 4 diam. 



Affinities. — This well-marked form has the doubly-bent, step- 

 shaped, interambulacral plates found in various Cyphosomoid 

 echinoids of the Middle and Upper Cretaceous, as in Cyphosoma 

 alcantarense, de Loriol.^ Its nearest ally is the Turonian C'optosoma 

 major (Coquand),^ which has a more granulate test, the two 

 scrobicular areas on each plate being separated by a line of granules, 

 and according to Cotteau's figures * the ambulacral plates consist 

 of five primaries. Gauthier ' included in his Cyphosoma sancti' 

 arromani a specimen shown in his figures 9, 10, and 11, which 

 is another ally of this species ; it has the step - shaped inter- 

 ambulacral plates, but the secondary tubercles are on a somewhat 

 different plan. C. sancti-arromani is from the Dordonian (i.e^ 

 Maastrichtian or uppermost Senonian) of Southern Tunis. 



^ From Jebel Gunneh, the locality of the t)'pe-specimen. 



2 P. de Loriol : Faune Cret. Portugal, vol. ii (1887), E'chinod., p. 52, pi. is., 

 tig. 4, from Up. Carentonian. 



* Phymosoma major, Coquand, 1863 : Geol. et Pal. Constantine, Mem. See. 

 E'mul. Provence, vol. ii, p. 256, pi. xxvii, figs. 16, 17- 



* Cotteau: Pal. fran9., Terr, cret., vol. vii (1864), pi. 1143, fig. 5. 



5 Gauthier: E'ch. foss. Sud Hauts- Plateaux Tunisie, pi. v, figs. 9-11,. 

 mn figs. 8, 12, 13. 



