518 Bibliographical Notice. 



By far the greater portion of the specimens described in the work 

 were derived from the area in the neighbourhood of Richmond 

 which Mr. Fontaine distinguishes as the " Richmond Coal-field," 

 as it is the most important district and contains nearly all the 

 workable coal in the Mesozoic strata of Virginia. Considerable 

 difficulty has been experienced in collecting specimens, as few 

 openings have been made in the strata for many years ; hence the 

 specimens had in great measure to be collected from old and 

 weathered refuse-heaps. Thus the work of securing good examples 

 has been one of great labour. 



As typical of the older Mesozoic areas of Virginia and as the most 

 completely explored, the geology of theEichmond Coal-field is more 

 fully described than that of any of the other areas. It contains 

 several valuable coal-seams, but their number and thickness vary 

 much in different parts of the field. There are, however, two im- 

 portant seams which appear to be persistent ; of these the lower, 

 called the main or big seam, is the most valuable, and though varying 

 greatly in thickness and often dividing into two seams, attains at 

 Clover Hill a varying thickness of from 15 to 26 feet. 



The second part of the work comprises the description of the 

 fossil plants, in which two new genera are created and many new 

 species described. One of the new genera is named Mertensides, 

 from the similarity of the individuals it embraces to the Mertensict 

 group of the Gleicheniacese ; but the ferns it includes differ in not 

 showing the characteristic dichotomy of the Mertensia. The type 

 of this genus is Mertensides (^Pecopteris) SiJZaiifS, Bunbury, sp. The 

 other new genus is Pseudodanaopsis, containing ferns with a Dicty- 

 opteroid nervation, but which also in some of their characters 

 approach to Heer's Danceopsis. It contains two species, Pseudo- 

 danaopsis reticulata and P. nervosa. 



Among the new species, LoncJiopteris virginiensis is of special 

 interest. The genus Loncliopteris was formerly regarded as Palaeo- 

 zoic, and only known to occur in the Coal-measures ; but in Lon- 

 cliopteris virginiensis there is one of the most handsome species of 

 the genus, which is now shown to extend upwards to the Ehsetic. 

 In all forty-two species of plants are described from the older Meso- 

 zoic rocks of Virginia; of these, twenty-one are peculiar to the 

 locality, four are either found in the Trias or allied to Triassic forms, 

 eight are similar to plants found in the Jurassic or allied to plants 

 occurring in rocks of that age, and twelve are either found in the 

 Ehsetic or allied to plants of that formation. 



The third part of the work is devoted to the older Mesozoic 

 flora of North Carolina, with the object of instituting a comparison 

 between its fossil flora and that occurring in the Virginian Mesozoic 

 area. Many of Emmons's species from North Carolina were, how- 

 ever, inaccurately determined; hence it was necessary for Mr. Fontaine 

 to enter into a critical examination of Emmons's species, and as far 

 as possible to correct his determinations. In the treatment of this 

 difficult pait of his subject Mr. Fontaine has acted most fairly, for 

 he gives in Emmons's own words the descriptions of that writer's 



