1851. _Sphenopteris nephrocarpa_, Bunbury, Quart. Journ. Geol. Soc. Vol. VII. p. 129, Pl. XII. fig. 1. 1876. _Thyrsopteris Murrayana_, Heer, Flor. Foss. Arct. Vol. IV. (2) p. 30, Pls. I. II. VIII. The above list represents a small selection of the names applied to Jurassic ferns from different localities which there are good grounds for regarding as referable to a single type[904]. Frond tripinnate; pinnae linear acuminate, attached to the rachis at a wide angle; the pinnules vary considerably in size and shape; in some the lamina is divided into a few broad and rounded lobes (fig. 275, B) while in others the leaflets are dissected into narrow linear segments. The sori are borne at the ends of veins; the fertile pinnules have a much reduced lamina and, in extreme cases, bear a close resemblance to those of _Thyrsopteris elegans_ (fig. 229, A, p. 294). The sori are partially enclosed in a cup-like indusium and the sporangia appear to have an oblique annulus. Venation and habit of frond of the _Sphenopteris_ type. [Illustration: FIG. 271. _Coniopteris hymenophylloides_ (Brongn.). Nat. size. From a specimen in the Manchester Museum.] The pinna shown in fig. 271 is the type-specimen of _Sphenopteris arguta_ Lind. and Hutt. from the Yorkshire Inferior Oolite and is indistinguishable from the English examples on which Brongniart founded his species _S. hymenophylloides_. Fig. 272 shows a specimen from the York Museum illustrating the difference between the sterile and fertile pinnae. The resemblance of some fertile pinnae of _Coniopteris hymenophylloides_ to those of _Thyrsopteris elegans_ has led to a frequent use, without any solid justification, of the generic name of the Juan Fernandez fern for Jurassic and Wealden plants. It is not impossible that some of the fossils described by Heer from Jurassic rocks of Siberia[905] as species of _Thyrsopteris_ are Cyatheaceous ferns, but it is impossible to say with certainty that they are generically identical with the recent species. In his monograph of the Potomac flora of Virginia[906] and Maryland, Fontaine has described as species of _Thyrsopteris_ several specimens of fronds which afford no evidence as to the nature of the sori or sporangia. Some of the fronds referred by this author to _Thyrsopteris rarinervis_[907], which I examined in the Washington Museum, are in all probability examples of _Onychiopsis_, a genus included in the Polypodiaceae. The fragments described by Lester Ward[908] as species of _Thyrsopteris_ from the Lower Cretaceous of the Black Hills of North America afford no satisfactory evidence of relationship to the recent type. Similarly Velenovský has described a Lower Cretaceous _Onychiopsis_ from Bohemia[909] as a species of _Thyrsopteris_, although the fertile segments bear little or no resemblance to those of the Cyatheaceous genus. Some fertile portions of fronds described by Heer[910] as