BibUograplncal Notice. 477 



in the determination of fossil plants. External resemblances raaj- 

 easily deceive the inexperienced student, as shown by examples in 

 figs. 20, 21, and 22. The venation characters are often doubtful as 

 tests in family or generic affinity, and even for larger groups, as 

 classes. Decorticated or otherwise imperfect casts of stems present 

 difficulties, some of which receive interesting explanations at 

 pages 102-105. Thus, the bark of one species of Lepidodendron is 

 stated to have been described with twenty-eight specific names, 

 under several genera. Lj/r/inodendron, Artisia, Steniherrjia, and 

 Tylodendron have been referred to mere peculiarities of structure 

 represented by casts. Contemporary insects, boring holes in plants 

 before they were fossilized, have left their minute coprolites in 

 abundance, easily mistaken for spores of cryptogams. 



Some cautious, sound, well-timed, and therefore useful remarks 

 on nomenclature and terminology, for the advantage of neophytes 

 and others, close this chapter and Part I. of the book. 



Part II. of this volume is occupied by descriptions of the plants 

 constituting the lower divisions of the Vegetable Kingdom and the 

 geological conditions under which they are met with. They are 

 taken in their natural sequence, beginning with the lowest. 



The Thallophyta (pp. 116-228) supply :— I. The Peridiniales, 

 represented h\ Peridinium pyrophorum^YhYQuhQvg-, II. The Cocco- 

 sphercs and Pihabdospheres, so common in the Chalk as well as in 

 the ocean, are described as organisms of doubtful affinity, but 

 probably algal (p. 121): III. The Schizophyta comprise (1) the 

 Schizophycese (Cyanophycese) and (2) the Schizomycetes. The 

 former are " fission-plants " or '' blue-green algae,'' and the latter are 

 " fission-fungi." 1. The formation of many calcareous oolitic con- 

 cretions is intimately connected with the presence of Chroococcaceae 

 and Xostocacese, members of the Schizophyceae ; and probably the 

 Girvanella, a simple tubular organism to which oolites in several 

 rocks are attributed, as also the Zonatrichites, may belong to this 

 group. The building-up of both calcareous and siliceous sinters is 

 regarded by some as due to the presence of some such low-class, 

 filamentous, and gelatinous alga5. There are also minute boring 

 algae belonging to this group, which perforate and burrow in corals, 

 moUuscan shells, and fish-scales ; and their analogues are found 

 fossil, besides lielping to reduce these hard substances to debris, 

 and, on the contrary, building up calcareous rocks, Cyanophyceae 

 have been probably efficient agents in preparing the mass of hot 

 volcanic ashes in the island Krakatoa for the growth of highly 

 organized plants, by occupying and modifying the surface under 

 conditions which would be fatal to more complex types. 



2. The Bacteria belong to Schizomycetes ; and a most careful 

 and cautious account of the researches that have led to the specifi- 

 cation of Micrococcus and Bacillus, as well in the fossil remnants of 

 ])lant8 that have suffered decomposition, as in coprolites of fish and 

 reptiles (pp. 1 32-138), deserves attentive consideration. The 

 possible error of mistaking spherical particles and rod-like bodies 

 due to incipient crystals in calcareous and siliceous mineralization 



Anrt. c&- Mag. N. Hist. 8ev. 7. Vol i. 35 



