678 PROF. J. W. GREGORY ON [NOV. I9II, 



Echinolampas, provisionally referred to as E. chericherensis. This 

 species is widely scattered over the plateau east, west, and south of 

 Cyrene, around Slonta and Messa, and it occurs nearly as far west 

 as the Wadi Gharib ; and a few specimens were found on the 

 escarpment to the north of Cyrene. This fauna also includes 

 Scutella tenera and a new species of Amphiope. Despite the 

 presence of the last genus, the age of the fauna is probably Upper 

 Eocene. 



The lowest Echinoidea were found in the Fibularia Bed at the 

 foot of the Cyrene escarpment and in a somewhat lower limestone 

 containing many eel ' \ spines and scattered plates ; both beds 

 are Middle Eocene. rocks, which on stratigraphical evidence, 



as well as that of the niollusca and foraminifera, are the oldest in 

 Cyrenaica, yielded no determinable echinoids. 



The geographical affinities of the fauna are with those of the 

 Mediterranean Basin. The Upper Eocene (Priabonian) echinoids are 

 found also in Tunis and Italy ; the Aqnitanian in Malta and Italy ; 

 the Fibularia, the one determinable Middle Eocene species, occurs 

 in Egypt; but the rich Echinoid faunas of the Middle and Lower 

 Eocene of Egypt are otherwise not represented in the collection. 

 Their absence is probably due to the fact that the beds deposited 

 during those periods in Cyrenaica were laid down in a deeper 

 sea. iSone of the species of the corresponding beds in Western 

 India have been recognized, although the faunas have certain 

 features in common. 



Depth of the Formations, as indicated by the Echinoidea. 



The echinoid faunas show by the rarity of the massive Clypeasters, 1 

 common in many of the Mediterranean Oligocene and Miocene 

 limestones, that the Cyrenaican rocks were deposited under some- 

 what deeper water than that in which the Clypeaster Beds of Malta 

 and Italy were laid down. 2 



The approximate ranges in depth indicated by the echinoids 

 for the formation of the limestones containing them would be 

 from 10 to 50 (or perhaps 100) fathoms for the Miocene limestones 

 east of Benghazi ; probably not more than 150 or 200 fathoms 

 for the Ecliinolampas Bed in the Priabonian ■ perhaps as much 

 as 250 to 500 fathoms for the Schizaster-ederi and ,8arsella- 

 lamberti Bed at Cyrene. The Fibularia Marl might be deeper, as 

 F. australis ranges down to 950 fathoms ; and the absence of 

 echinoids, except delicate spines, in the chalky beds of the Apollonia 

 Limestones might indicate for those rocks a depth of perhaps 

 1000 fathoms. 



1 Fragments of a thick Clyjjeaster were found at Birlibah, Gubah, and in 

 several exposures on the coastal plain about 12 to 15 miles east of Benghazi. 



2 The depth at which the massive Clypeaster humilis Ag. was obtained by 

 the 'Challenger' ranged from 15 to 20 fathoms; see A. Agassiz, 'Report 

 on the Echinoidea ' Chall. Exped., Zool. vol. iii, pt. i (1881) p. 119. The 

 range of Clypeaster and Echinanthus (sensu A. Agassiz) is given on p. 215 of 

 the same Report, as down to 120 fathoms. 



