Reviews — Recent and Fossil Entomostraca, 519 



and Peroxide of iron, Silicate of iron, Oxydulous iron, Manganese, 

 Iron pyrites. 



Class IV. Roches a base combustible. Families, Sulphur, Dysodile, 

 Asphaltum, Graphite, Anthracite, Coal, Lignite. 



The families are again divided, as they are either Aggregates, 

 Conglomerates, or Detrital, and the former as they present either a 

 Phanerogenous or Adelogcnous structure. — J.M. 



II. — Recent and Fossil Entomostraca. 



1. A Monograph of the Recent British Ostracoda. By G-. S* 

 Brady. 4to. with 18 Plates. 1868. (From the Transactions of 

 the Zoological Society.) 



2. BivALVED Entomostraca, Recent and Fossil. By Prof. T. 

 Rupert Jones. 8vo. 1868. (From the Quarterly Journal Mi- 

 croscop. Science.) 



3. Notes on the Paleozoic Bivalved Entomostraca : No. YIII. 

 Some Lower-Silurian Species from the Chair of Kildare, 

 Ireland. By T. Rupert Jones and Dr. H. B. Holl. (From 

 the Annals and Mag. Nat. Hist.) 



OF the many kinds of minute creatures that leave their shells or 

 skeletons in muds, sands, shell-beds, and coral-reefs, to become 

 integral constituents of clays, limestones, and other strata, few, 

 except Foraminifera, contribute so large a proportion of calcareous 

 matter as the little bivalve carapaces of the Ostracodous and PJiyl- 

 lojpodous groups of the Entomostraca. This has long been known, 

 and numerous notices and monographs, often furnished with many 

 good figures, have been published within the last twenty years, 

 illustrating the many diiferent forms of Bairdia, Cypris, OytJiere, 

 CytJierella, Cypridiiia, Beyricliia, Leperditia, Estheria, and other 

 genera belonging to these low types of Crustacea. The difficulty 

 of correctly assigning the fossil carapace -valves to definite specific 

 and even generic groups, has been dwelt upon in the monographs on 

 the Cretaceous and Tertiary Entomostraca, and of the fossil EstJierice, 

 by Prof. Jones, which were published by the Palseontographical 

 Society, and nothing but careful and extensive examination of living 

 specimens, and exact comparison of the limbs and internal organs, 

 as well as of the carapace -valves, could furnish good grounds for 

 either the collocation of apparently similar forms of fossil valves, or 

 the specific separation of some that presented differences of outline, 

 ornament, and other features. Mr. Gr. S. Brady's assiduous study of 

 the Bivalved Entomostraca, supplementing, and indeed greatly aug- 

 menting, the information given to naturalists on this subject by 

 Baird, Norman, Sars, Liljeborg, and others, has eventually put us in 

 possession of a considerable store of facts, illustrating the relation- 

 ship of a multitude of these little organisms, and enabling us to 

 speak more definitely than heretofore of the probable generic and 

 specific groups to which our fossil Entomostraca are referable. It is 

 not alone in the monograph mentioned at the head of this article 

 that Mr. Brady's researches are to be studied, for in the Trans- 



