Notices of Memoirs — Perim Island. 133 



The specimens sent are all from volcanic rocks. The surface, 

 according to Captain Eupert Jones, is composed mostly, to a depth 

 of about 7 feet, of loose blocks (4 feet or less in diameter), often 

 imbedded in calcareous sand or mud. The underlying rock is 

 exposed in cliffs and in quarries, and occurs generally in roughly 

 horizontal layers. One mass in situ (near Balfe Point) is a not 

 very basic basalt (almost an andesite) crowded with felspar microliths 

 with marked fluidal orientation, and is probably a lava-flow. Another 

 reddish rock with scattered rounded vesicles (from a cliff north-east 

 of the harbour) approaches a microcrystalline basalt in character, 

 and consists of much plagioclase, clear gum-like augite, some red- 

 brown ferruginous olivine or pyroxene, and a little black speckled 

 glassy base. In another spot (near Balfe Point) a whitish tuff or 

 fine agglomerate is quarried, and consists largely of fragments of 

 pumice with some broken felspar, augite, and other crystals. 



The surface blocks in one or two examples consist of fragmental 

 rocks. One is a red, more basic tuff, containing thin black streaks, 

 apparently of a spherulitic glass. The blocks, however, are mostly 

 scoriaceous and vesicular, petrologically generally basaltic, and 

 similar to the underlying rocks described above, but with, some 

 variation, as if they might represent a broken lava crust. They 

 are crossed by veins of calcite, and the ashy materials and other 

 fragments are often cemented by calcareous deposits. 



The history of Perim Island belongs mainly to the Tertiary era. 

 We may infer that the Eed Sea, from its general contours and the 

 steep descent of the bed towards a central depression, forms part 

 of the Great Rift Valley, extending from Lake Tanganyika to the 

 Jordan, along which at so many places volcanic outbursts on a large 

 scale have occurred. Both in Arabia and in Abyssinia extensive 

 tracts of volcanic rocks are found of more than one period. The 

 rocks of Perim belong probably to the later or so-called Aden group. 

 The raised beaches of the island are an evidence of oscillations of 

 level, which are proved by upraised and submerged coral reefs to 

 have affected other parts of the Red Sea. Denudation and weathering 

 of the surface took place, and calcareous sediment was deposited, 

 while at different times coral reefs became established in the adjacent 

 shallow seas. 



IR, E "v^ I IE ~W S. 



I. — Catalogue of the Fossil Fishes in the British Museum 

 (Natural History). By Arthur Smith Woodward, LL.D., 

 F.R.S., F.G.S. Part IV : pp. xxxix, 636, with 19 Plates and 

 22 Figures. 8vo. (London, 1901.) 



DR. A. SMITH WOODWARD and the Britisli Museum are to 

 be congratulated on the completion of this important memoir 

 on Fossil Fishes, the fourth volume of which has been for long 

 anxiously expected by all Ichthyologists. For those specially at 

 work among the fossil forms, it will be a welcome and an indispensable 



