ON THE GEOGRAPHY AND GEOLOGY OF THE ATLAS RANGES. 167 



Briefly stated, my exploration of the monntains between Demnat and 

 the sea show that they consist — 



(1) Of a central core or nucleus of metamorphic slates and crystalline 

 limestones, at places much disturbed by intrusive bosses, dykes, and 

 veins of porphyrites, basalts, and diorites. 



(2) Of an enormous series of red and purple shales, marls, and sand- 

 stones forming the great mass of the chain, at some points, as at Taurirt, 

 rising to an elevation of even 11,000 feet. These, as far as can be ascer- 

 tained, belong to the Cretaceous series. 



(3) Of an upper series of Cretaceous cream and grey- coloured lime- 

 stones and sandstones, with fossils at places, among which have been 

 determined Trigonia, Area, Rhynchonella, Astrea, Gryphma, Astarte, and 

 I/ucina. These series attain but a small development in the Atlas, as 

 compared -with the lower series, and are to be found only in the lower 

 outer mountain terraces or steps. They are characterised by numerous 

 intrusive bosses and great dykes of amygdaloidal basalts, which break 

 through them along the whole length of the mountains from Demnat 

 westward. In the plateau of Southern Morocco the red shales and sand- 

 stone series are masked by the limestones, except where some disturbance • 

 has brought the former to the surface. 



(4) Of later formations nothing has been satisfactorily determined. 

 Of glacial deposits there were little more than indications at the heads of 

 some of the glens, and at one or two places in sheltered nooks, as in the 

 glen of the Wad Nyfis. Slightly more important accumulations were 

 observed in the valley of Giudafy, Wad Nyfis, and in the glen of the 

 Urika. Moraines were detected between the Wads Gadat and Mi&fiwa ; 

 and in the Valley of Telnet. On the Plain of Morocco transported 

 boulders were remarked. Upon the whole, evidences of glaciation were 

 insigniBcant, and in those parts I explored I saw nothing anywhere in 

 any way comparable to the enormous deposits described by Maw, of the 

 soundness of whose conclusions as to their being: of srlacial origin I have 

 the gravest doubt. 



III. Botany. — On the botany of the expedition I have little to say, 

 beyond explaining the extreme smallness of the collection brought back — 

 a list of which, drawn up at Kew, accompanies this report. The whole of 

 the time spent in the mountains was in the very driest and hottest season 

 of the year, when for nearly eight months scarcely a drop of rain falls. The 

 consequence is that the mountains, even to the highest points, are quite 

 bare, and only along the courses of the streams are any plants to be found. 

 I left Morocco just as the first autumnal rains began to fall. 



Very much the same remarks apply to the collection of beetles. A 

 list of specimens secured is appended. 



Geology. 

 Atlas Expedition. Joseph Thomson. 



Asif-el-Mel, Marossa. — Hard cream-coloured limestone, largely com- 

 posed of casts of shells, badly preserved, among which Triyonia and Area 

 seem to be most abundant, but none are specifically determinable. Pro- 

 bably of Oolitic age. 



District of Ait Musa, Mtuga. — Hard dark limestone, weathering red 

 and brown, filled with large globular Rhynchonellee, much resembling 

 B. tetrahedra. Possibly Liassic. 



