Br. J. W. Gregory — Egyptian Echinoidea. 151 



Figures. — PL V, Fig. la, test from the side; 6, from above. 

 Fig. Ic, two ambital iaterambulacral plates, X 2 diam. Fig. \d, 

 two ambital ambulacral plates, x 4 diam. 



Affinities. — This echinid is most nearly allied to UhahdorAdaris 

 itala (Laube),^ which has been described from the Egyptian Eocene 

 by M. de Loriol-le-Fort. The principal difference between them 

 is that in B. itala the tubercles are non-crenulate, whereas in 

 B. Libyensis they are strongly crenulate. The tubercles are also 

 taller. The shape of the test is more like that of B. Zitteli, Lor.,^ 

 but in that species the granulated areas of the interambulacra are 

 much more restricted. 



The third echinid with which it must be compared is Porocidaris 

 Schmideli (Miinst.),^ with which it agrees in the crenulation of the 

 tubercles. But the new species has not the slits around the bases 

 of the mamelons ; the interambulacral plates are much taller ; in 

 a British Museum specimen (No. 75,669) of P. Schmideli the height 

 of the ambital plates is to the width as 9 : 13 ; and in P. Schmideli 

 the epistroma consists of coarser and more uniform granules. 



Genus PSAMMECHINUS, L. Agassiz, 1846. 

 1. PsAMMECHiNus Ddciei, Wright, 1855. 



Synonymy. — See Gregory, " Maltese Echinoidea" : Trans. Eoy. Soc. 

 Edinb., vol xxxvi (1891), p. 590. 



Distribution. — tip. Miocene — Tortonian : Malta. Mid. Miocene — 

 Helvetian: Egypt; Coll. Geol. Surv. Egypt, No. 822. 



There is a broken specimen of a Fsammechinus in the collection 

 which agrees in the characters shown with this well-known Maltese 

 species. The granulation of an ambital plate of the Egyptian 

 specimen is shown on PL V, Fig. 3. The species has not pre- 

 viously been recorded from Egypt. An allied African species is 

 P. Soubellensis, Per & Gauth.,^ in which, however, one tubercle on 

 each interambulacral plate is much larger than the rest of the 

 horizontal series. 



2. Psammeohinus Lyonsi, n.sp. 



Diagnosis. 



Test small ; somewhat conical above, with tumid, well-rounded 

 sides. Base flat. Seen from above the shape is sub-pentagonal, 

 but with well-rounded angles. 



Ambulacra. — Each ambulacral series consists of about thirteen 

 plates, each of which bears a single conspicuous tubercle. The 

 pore pairs are arranged in well-curved triplets. • A double series of 

 miliary granules runs down the middle of each area. The scrobicular 

 areas of adjacent plates in the same vertical series are confluent. 



1 Cidaris itala, G. C. Laube, " Ech. vicent. Tert. Geb. " : Denk. Ak. Wiss. 

 Wien, vol. xsix, pt. 2 (1869), p. 9, pi. i, fig. 3. 



2 De Loriol, 1883, Beitr. libyscli. Wiiste, vol. ii, pt. 1, p. 8, pi. i, figs. 1,11. 



■* Cidarites Schmidelii, Miinster, in Goldfuss, Petref. Germ., vol. i, p. 120, pi. xl, 

 fig. 4. De Loriol, 1883, op. cit., p. 9, pi. i, fig. 10. 



* Perou & Gauthier, Ech. loss. Alger., vol. iii, fasc. 10 (1891), p. 252, pi. v, 

 figs. 1-4. 



