E. H. Sellards — Codonotheca. 93 



prove to fall witlnn the comparatively varied but less well- 

 known Cycadoiilices, as representative of a specialized division 

 at present included in that group and which has suffered extinc- 

 tion. The plants to which the Codonotheca tyj^e of fructification 

 belongs, as far as the arrangement of their spore-bearing organs 

 is concerned, seem to have reached a comparatively specialized 

 condition as early as the Upper Carboniferous. There are 

 present in the Coal Measures and at the Mazon Creek locality 

 several genera or groups of plants, the fructification of which is 

 either unknown or but im|)erfectly understood. Conspicuous 

 among these, both from its large size and great abundance, is 

 J^eiiropteris^ especially the large species, N. decipiens Lesqx. 

 Kenault^ and others have shown that the petiole of Neurop- 

 teris as well as that of Alethoj)teris^ possesses the Myeloxylon 

 type of stem structure. The Medulosese to which Myeloxylon 

 belongs are regarded as a divergent branch of the Cycadofilices.f 

 The only information regarding the fructification is that 

 obtained by Kidston from a specimen of N, heterophylla, a 

 species of the small-pinnuled division of the group. :j: Kidston's 

 material was unfortunately poorly preserved, but served to 

 indicate that the fronds were dimorphic, and that the spore- 

 bearing organs were grouped in clusters at the ends of the 

 slender petioles. There is reason for believing that the entire 

 Xeuropterid groujD was dimorphic. As a rule, those plants 

 having the sporangia on the under side of the fronds, after the 

 manner of ordinary ferns, not infrequently preserve impressions 

 of the sporangia and sori. Neuropteris is abundant through- 

 out the Coal Measures, and very large collections of IS'europ- 

 terid fronds have been examined by various paleontologists 

 without finding evidence of sporangia. The large fronds of 

 NeuTopteris would doubtless supply a considerable number of 

 detached pinnules as compared with the number of fertile 

 spore-bearing parts, however these may have been arranged. 

 In the Yale University Museum collection, the proportion 

 between Codonotheca caduca and Neuropteris decipiens is 

 approximately one of the former to ten of the latter.§ [N'ever- 

 theless, the fact should not be lost sight of that there are a 

 number of other plants in the Coal Measures to any one of 



*Eenaiilt, Affinites botaniques du genre Neuropteris, Coraptes rendus, 

 vol. Ixxxiii, pp. 899-401, 1876. 



f Scott, Studies in Fossil Botany, pp. 394-396. Compare also Solms-Lan- 

 bach, tJber Medulosa Leuckarti, Bot. Zeitung, Bd. Iv, Heft x, pp. lTo-202, 

 1897. 



t Trans. Eoy. Soc. Edinburgh, vol. xxxiii, pt. i, p. 150, pi. viii, fig. 7, 

 1887. 



§ The relative proportion, as here given, is based on the Yale collection 

 from Mazon Creek, which contains 75 specimens of Codonotheca to some 1,200 

 of Neuropteris, 750-800 of which are Neuropteris decipiens. 



