XXVIlJ ALETHOPTERIS 573 



obtained by Lyell ^ from the Coal-Measures of Nova Scotia, in 

 the smaller size of the meshes. Linopteris obliqua occurs in the 

 Upper and Middle Coal-Measures of Britain; it is recorded by 

 Zeiller from Asia Minor, by Lesquereux^ from Pennsylvania, 

 and by other authors from several European localities. The 

 pinnules frequently occur detached from the frond and like 

 those of some species of Neuropteris were caducous. Linopteris 

 is rare in British strata. 



Fig. 374. Linopteris neuropteroides,G\x\h. (Pinnule of type-specimen. Enlarged. 

 After Zeiller.) 



Alethopteris. 



The name Alethopteris, instituted by Sternberg*, is applied 

 to compound fronds often reaching a considerable size, exhibiting 

 the following features : 



The linear pinnules are attached by the whole breadth of the base, 

 with the lower edge of the lamina decurrent and usually continuous with 

 that of the next pinnule (figs. 290, A, p. 399 ; 375). The ultimate segments- 

 are entire, with an acute or rounded apex and often characterised by a fairly 

 thick lamina convex on the upper surface. From a prominent midrib, 

 continued to the apex of the pinnule, numerous simple and forked secondary 

 veins are given oflF at a wide angle, the decurrent portion of the lamina 

 being supplied by veins direct from the axis of the pinna. _ In the upper 

 part of a frond or primary pinna the pinnules may be replaced by a 

 continuous, lobed, or entire simple lamina. The main rachis occasionally 

 exhibits dichotomous branching, but the fronds are for the most part 

 constructed on the pinnate plan. Single Cyclopteroid pinnules* occur on 

 the petiole of some species of the genus. 



1 LyeU (45) A. Vol. ii. p. 202. " Lesquereux (80) A. p. 146. 



3 Sternberg (26) A. * Grand'Bury (04). 



