On Fossil Plants of the Coal-measures. 403 



muscle is cutaneous and springs from the upper part of the pla- 

 tysma : 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 arrange- 

 ment 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. 



•* Notice of further 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.) 



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 Burntisland, 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 cylinder, 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 central 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 expand- 

 ing 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 considerable dimensions ; but the entire vascular 

 system always remains small, compared with the diameter of the 



