1872.] 



On the Fossil Plants of the Coal-measures. 



95 



the upper part of the platysma : he has also been able to show that the 

 abdominal pectoral is not part of the pectoralis minor. 



By dissecting a large number of species, the author has been able to 

 correct a number of errors in the hitherto-published records of the myology 

 of the Cheiroptera — such as the origin of the fourth pectoral, the insertion 

 of the latissimus dorsi, the arrangement of the forearm-muscles, &c. 



Although the general plan of the muscular system is the same in all the 

 species, yet there are very many suggestive varieties ; and from a comparison 

 of their muscles, it would seem that each of the four great groups of 

 Bats is characterized by a slightly different arrangement of muscles. 



The author has, for purposes of brevity, carefully abstained from adding 

 any thing of theoretical deduction to this paper, which he has endeavoured 

 to confine to a simple statement of anatomical facts. 



III. "Notice of farther Researches on the Fossil Plants of the Coal- 

 measures." By Dr. W. C. Williamson, F.R.S., in a Letter to Dr. 

 Sharpey, Sec. R.S. Received November 17, 1871. 



Owens College, Manchester, Nov. 16, 1871. 

 My dear Dr. Sharpey, — Since I read my last communication to the 

 Royal Society on the organization of the Fossil Plants of the Coal-measures I 

 have done a large amount of work, having cut between two and three hundred 

 new sections and with most satisfactory results. I have obtained a series 

 of specimens almost completing the life-history of one plant from Burn- 

 tisland, beginning with the tips of the smallest twigs and ending with the 

 large stems. The former are mere aggregations of parenchyma with a 

 central bundle of barred vessels mixed with a small amount of primitive 

 cell-tissue. As the twig grew the leaves assumed definite form, and the 

 central vascular bundle opened out at its central part, so as to form a cy- 

 linder, the interior of which was occupied by parenchyma. This cylinder 

 grew rapidly, the number of its vessels steadily increasing ; but they were 

 all equally arranged as in, what I have termed, the medullary vascular cy- 

 linder, i. e. not in radiating series. We thus obtain the origin of that 

 remarkable cylinder, and see that it is the expanded homologue of the cen- 

 tral vascular bundles of the living Lycopods. Whilst these processes were 

 in progress the cortical portion became differentiated into layers, and the 

 parenchymatous cells of the pith continued to multiply, so as to occupy 

 the expanding interior of the vascular cylinder. After attaining a certain 

 size, through the above processes, a new element of growth appeared ; an 

 exogenous addition was made to the exterior of the cylinder, also consisting 

 of barred vessels, but these are arranged in the radiating series described in 

 my last memoir. This series continued to grow until it attained to consider- 

 able dimensions ; but the entire vascular system always remains small, com- 

 pared with the diameter of the stem, the chief bulk of which consists of 



