Reviews — Mesozoic Plants of England. 615 



of regional metamorphic character are valuable for ornamental 

 purposes. 



The observations of the author of the paper under review show, 

 however, that these distinctions cannot be maintained. Nor does he 

 agree with Vogt in regarding certain minerals (garnet, vesuvianite, 

 scapolite, wollastonite, pyroxene, amphibole, epidote, chondrodite, 

 felspar, tourmaline, spinel, etc.) as characteristic of contact-meta- 

 morphic limestones, and others (quartz, actinolite, mica, talc, chlorite, 

 rutile, hematite) as occurring in limestone of regional metamorphic 

 origin. According to our author, however, the accessory minerals 

 do fall into two groups, the first, including garnet, wollastonite, 

 vesuvianite, diopside, periclase, and spinel, being characteristic of 

 limestones altered by normal contact-metamorphism, and the second, 

 including quartz in rounded grains, and members of the mica, 

 chlorite, amphibole, and epidote groups, and also corundum, occurring 

 in limestones altered by pz'ezo-contact-metainorphism (contact-meta- 

 morphism accompanied by pressure) ; here the carbon dioxide being 

 unable to escape, the formation of wollastonite is impossible, and 

 denser minerals are formed in place of lighter ones, corundum 

 e.g. replacing spinel. On the other hand, phlogopite, forsterite, 

 epidote, and pyrrhotite occur with either group of contact-meta- 

 morphosed limestones. [This classification does not exactly apply 

 in Ceylon, where, in spite of the absence of wollastonite, spinel is 

 not replaced by corundum.] All the minerals so far mentioned result 

 from the alteration of matter present in the original limestone ; 

 magnetite and ilmenite are also primary minerals. 



Other minerals — tourmaline, scapolite, apatite, fluor, topaz, and 

 some mica — are probably of pneumatolytic origin, and derived from 

 the intrusive magma ; and so with pyrites, hematite, and sphene. 

 Some lime-bearing silicates — particularly garnet, wollastonite, 

 diopside, actinolite, etc., when they occur in concretionary nodules 

 and layers near to the intrusive rock — may also be of external 

 origin, and not merely developed from materials originally present 

 in the limestone. 



The author considers that the granular limestones and dolomites 

 are without exception of organic origin, and that — at any I'ate in 

 the vast majority of cases — their mineral composition and crystalline 

 structure are the results of contact-metamorphism. The paper ends 

 with a list of the accessory minerals that occur in crystalline lime- 

 stones and dolomites. A. K. 0. 



III. — Catalogue of the Mesozoio Plants in the Department 



OF Geology, British Museum (Nat. Hist.). The Jurassic 



Elora, II : Liassic and Oolitic Floras of England (excluding the 



Inferior Oolite Plants of the Yorkshire Coast) . By A. C. Seward. 



pp. 192, pis. xiii, text-figs. 20. 1904. 



fl^HIS volume constitutes the Second Part of the Catalogue of 



X Mesozoic Plants in the British Museum. The First Part, 



published in 1900 by the same author, dealt with the magnificent 



collection from the Inferior Oolite of Yorkshire. The present 



