On Medullosa pusilla. 



227 



Locality : Lark Hill Pit, Colne, Lanes. Horizon : Soap-stone, overlying 

 Halifax Hard Bed, Lower Coal Measures. 

 Found by Mr. P. Whalley, 1906. 



I have italicised the characters in which this form differs from M. anglica. 

 The distinctions are of little importance, with the exception of the small 

 size of the plant and the simpler structure of the hypoderma, points which 

 appear to be of some diagnostic value. 



The question arises whether it is worth while to separate the species from 

 M. anglica on these somewhat slender grounds. The difference in size is 

 considerable, and not due merely to age, for secondary growth is already 

 fairly advanced, while the whole primary structure is on a small scale. 



The specimen might, however, be from the basal part of the stem, where it 

 had not reached its full dimensions, or might belong merely to a dwarfed 

 plant. At the same time, it is perhaps equally probable that our specimen 

 represents a distinct species. There is strong reason to believe that the 

 foliage of M. anglica was of the AlethopUris type (Scott, '99, p. 102), and it is 

 probable that the species may have been identical with A. lonchitica, so 

 abundant in the Lower Coal Measures. We have no evidence as to the 

 foliage of M. pusilla, but there is a certain presumption that it was also that 

 of an Alethopteris, both from analogy with M. anglica and from the older 

 observations of Eenault. That author, after a careful comparison, came, as is 

 well known, to the conclusion that it was extremely probable that the 

 petioles of his Myclopteris (Myeloxylon) Lanclriotii bore the fronds of certain 

 species of Alethopteris (Eenault, '83, p. 165). In his 1 Cours de Botanique 

 Fossile ' he reproduces the figure of M. Landriotii, var. a, under the title 

 " Section Transversale d'un Petiole Alethopteris " ('83, Plate 28, fig. 1). 

 This is the section which most closely resembles the leaf-base of M. pusilla. 

 If M. pusilla was the stem of an Alethopteris other than A. lonchitica, it may 

 conceivably have belonged to the closely allied but somewhat smaller plant, 

 A. decurrens, the only other species which appears to be frequent in the British 

 Lower Coal Measures.* This is a mere conjecture, but, at any rate, it is 

 reasonable to suppose that more than one Medullosa existed in our Lower Coal 

 Measure flora, and, as our specimen is quite peculiar in its small dimensions, 

 and has other slight distinctive characters, we may provisionally treat it as 

 representing a new species. 



My friend, Dr. Lotsy, has proposed to divide the genus Medullosa into two 

 new genera, Neuropteromedullosa and Pccopteromedullosa, the former having a 

 complex stelar system together with Ncuroptcris foliage, while the latter is 

 characterised by a relative simple stelar system (as in M. anglica) and the 

 * Kidston, '93, pp. 225, 245 ; Franke, '12, p. 42. 



