222 I^rof. J. W. Gregory — Fossil Echinoidea 



Figures. — PI. X, Fig. 6, abactinal view of a specimen, nat. size ; 

 Fig. la, another specimen from the side, nat. size ; Fig. 76, abactinal 

 end of an ambulacrum of the same, by 4 diam. ; Fig. 7c, an ambital 

 ambulacral plate of the same, by 4 diam. ; Fig. Id, interambulacral 

 ambital plates of the same specimen, by 4 diam. ; Fig. 8, aotinal 

 surface of another specimen, nat. size. 



Distribution. — Cretaceous (Cenomanian or Turonian) : east end of 

 Abu Roash village. L 1376. Collected by H. J. L. Beadnell, Esq. 



Affinities. — The species is allied to the Turonian Cyphosoma 

 ^oquandi, Cott.,^ of Batna, Algeria, in which the granulation is more 

 abundant, the scrobicular areas are not confluent, and there are only 

 five components in the compound, ambital, ambulacral plates. 



THYLECHINUS, Pomel, 1883. 

 1. Thylechinus quincuncialis,^ n.sp. (PI. XI, Figs. 8a-c.) 



Diagnosis. — Test above medium size ; circular ; depressed. 



Peristome moderate in size; circular with well - developed 

 buccal slits. 



Ambulacra : about 16 compound plates in each vertical series. 

 The scrobicular circles are very incomplete ; they may be represented 

 only by a series of granules round the edge of the boss, but there 

 may be a line above and below the boss, along the horizontal edge 

 of the plate. 



Interambulacra : about 13 plates in each vertical series. The 

 plates are slightly bent, the abactinal margin being concave. The 

 ambital tubercles are quincuncial in arrangement, and there are three 

 vertical series on each side of an interambulacrum at the ambitus. 

 The three plates nearest the peristome have one tubercle each. 



Dimensions : 



Diameter 30-31 mm. 



Height 12-13 mm. 



Distribution. — Cenomanian : Sinai, marls at the head of Wadi 

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



Figures. — PI. XI, Fig. 8«, a specimen from the side, nat. size ; 

 Fig. 86, part of the ambitus, showing the plan of the interambulacral 

 tubercles, by 3 diam. ; Fig. 8c, two compound ambulacral plates 

 from the same, by 4 diam. 



Affinities. — This species resembles by its quincuncial tubei'cles 

 one of the two echinoids included by Gauthier^ in T. sancti-arromani 

 (Gauth.), from the Dordonian (Upper Senonian) of Bir Maguer, 

 Southern Tunis. It appears to me probable that the specimen 

 illustrated by Gauthier's figs. 9-11 is a distinct species from his 

 figs. 8, 12, and 13, which may be selected as the type of the species. 

 Tliis ThylecMnus qtiincuncialis differs from T. sancti-arromani by the 

 presence of only one tubercle, instead of a row of smaller ones on 

 the plates next the peristome. 



1 Cotteau: Pal. fran?., Terr. cret. (1864), p. 587, pi. 1139, figs. 7-12. 

 - From the plan of the tuberculation. 



^ Ci/phosoma sancti-arromani, Gauthier, 1889: E'cli. foss. Sud Hauls -Plateaux 

 Tuuisie, pp. 81-82, pi. v, figs. 8, 12, 13, non figs. 9-11. 



