152 Dr. J. W. Gregory — Egyptian Echinoidea. 



Inter ambulacra of about ten plates in each vertical series. Each 

 plate bears a prominent tubercle. The miliary granules are abundant 

 and well developed. The scrobicular circles are complete, those on 

 the upper border of one plate completing the circle of the plate 

 above. 



Peristome very large ; branchial slits deep. 



Dimensions. 



mm. 



Height of test .'j"5 



Diameter of test ... ... ... ... ... ... 9-5 



"Width of ambulacrum at ambitus ... ... ... ... 3-5 



Width of iuterambulacrum at ambitus ... ... ... 2-3 



Diameter of peristome ... ... ... ... ... 4-5 



Distribution. — Mid. Miocene — Helvetian : Egypt ; Coll. Geol. 

 Surv. Egypt, Nos. 977, 988. 



Figures. — PI. V, Figs, ia and h, a test from the side and from 

 below, X 2 diam. Fig. 4c, ambital plates, x 8 diam. Fig. 5, 

 ambital plates of another specimen, x 8 diam. 



Affinities. — The species, by its unituberculate, multigranulate 

 interambulacral plates, belongs to the series of species which Pomel 

 grouped as the genus Arbacina ; while by the deep, narrow branchial 

 slits it is allied to the same author's Oligophyma. 



Its nearest ally is Psammechinus subriigosus, Pomel, ^ from the 

 Pliocene of Oran, in which the maraelon of the primary tubercles 

 is much larger, there are some secondary interambulacral tubercles, 

 and the ambital interambulacral plates are longer. 



Psammechinus lavior, Pomel," from the same deposits, has a more 

 scanty epistroma. 



The specimen illustrated by PI. V, Fig. 5, resembles the Arbacina 

 asperaia, Pomel, ^ from the Pliocene of Oran, but in tliat form the 

 tubercles have a much larger, flat mamelon, which is about 

 two-thirds instead of one-third the diameter of the boss. It also 

 resembles a small Persian Miocene Psammechinus affinis, Fuchs,* in 

 which the scrobicular circles are complete on each plate, so that the 

 adjacent scrobicular areas are separated by two lines of granules 

 instead of by only one. 



Oligophyma cellensis, Pomel, ^ is another ally, but that has a much 

 smaller peristome and longer, lower interambulacral plates. 



Genus COPTOSOMA, Desor, 1858. 



1. CoPTOsoMA Thevestense, Per. & G. 



Cyphosoma Thevestense, Peron & Gauthier, 1879 : " Ech. foss. Alger.," 



fasc. vi, p. 105, pi. xiii, figs. 5-8. 



Distribution. — Turonian : Tebessa, near Constantine, Algeria. 



Turonian (?) : Abu Koasch, Egypt ; Coll. Geol. Surv. Egypt, No. 50. 



1 Pomel, "Pal. Alger.," Zooph.,fasc. 2, Ech., livr. 1 fl885), pi. C, xii, figs. 1-4. 

 » Ibid., pi. C, xii, figs. 5-8. 

 3 Ibid., pi. C, xi, figs. 5-8. 



* Fuchs, "Tert. Ech. Persien" : Sitz. Ak. Wiss. Wien, vol. Ixxxi, pt. 1 (1880), 

 p. 99, pL, figs. 6-lG. ^ 



* Pomel, op. cit., pi. C, x, figs. 1-7. 



