Reviews — G. Merzbacher — On the Caucmus. 375 



Merzbacher's specimens are unfossiliferous, while some of the dark 

 schiefer contain numerous rutile needles ; this, however, is not 

 conclusive, and on the whole Dr. von Ammon is disposed to refer 

 them to the Jurassic period, to which one sandstone, from its 

 fragments of echinoderms, almost certainly belongs. But Herr 

 Merzbacher speaks in his narrative of schiefer which he regarded as 

 more ancient, so it is very possible (as I pointed out in 1896) that 

 these dark I'ocks may be, some of Mesozoio, some of an earlier date, 

 (c) The rocks of Laila come next, with which we may consider 

 (a) already mentioned. Laila (13,400 feet) is a peak to the 

 S.S.E. of Elbruz, but on the opposite side of the watershed. On it 

 Signer Sella in 1889 found some fragments of ciinoids. These, as 

 was explained in the appendix to Mr. Freshfield's book, were 

 considei'ed by Mr. Bather and Dr. Gregory to resemble most nearly 

 Balanocrinus, a subgenus of Pentacrinus, of late Cretaceous or 

 Tertiary age, while Herr Merzbacher, both then and now, placed 

 them very near JSxtracrhms subangularis, a Liassic species. Dr. von 

 Ammon, after examining some other specimens collected by his 

 friend, agrees with him in the identification and in referring the 

 rocks to the Lias. Fossils were also obtained at a spot in the heart 

 of Daghestan between Tindi and Aknada. Among them are joints of 

 a pentacrinus, which Dr. von Ammon figures, assigning it to a new 

 species, P. Merzbacheri, which is near to P. pentagonnlis (Goldf.), 

 and very probably belongs, like it, to the Callovien, or, at any rate, 

 the Middle Jura. A pecten was also found, which closely resembles 

 P. personatus (Goldf.), also a Jurassic form. Hence the upper part of 

 Laila is more probablj' composed of Jurassic than of Oretaceo-Eocene 

 rocks. (IV) With the younger eruptive rocks comes a specimen 

 from the western summit of Elbruz, obtained possibly at a slightly 

 greater elevation than that which I examined.^ Dr. von Ammon 

 seems to think my description too brief, but I believe that I omitted 

 nothing of importance, and doubt the utility of enlarging on trivial 

 details. His specimen, however, contains a little hypersthene- and 

 quartz, both of which are absent from mine. The rock of which 

 he gives an analysis contains 63-80 of SiOa, with a rather high 

 percentage of alkalies, viz. NaoO:=5-47 and K.,0 = 3-26, but 

 is not otherwise remarkable ; very probably the two specimens 

 represent slightly different ejections. He expresses a doubt whether 

 this peak is a broken crater, but the descriptions of earlier visitors 

 (a violent gale gave Herr Merzbacher little opportunity of making 

 observations) seem favourable to the idea. In any case he regards 

 the volcano as comparatively modern, thinking it may have continued 

 its eruptions even into the Glacial Epoch. The remaining specimens, 

 three in number, come from Kum-tube, a mountain rising from the 

 Tschegem-thal on the northern side of the watershed, some thirty 

 miles east of Elbruz. The volcanic rocks, which have been already 



» Proc. Roy. Soc, 1887, vol. xlii, p. 318. 



- I have again examiued my slice, but though a pyroxene is certainly (I said 

 possibly before) present in grains of rather variable size, most at any rate give an 

 oblique extinction. But I think it may also contain about two flakelets of biotite. 



