DESCRIPTION OF SPECIES. 47 



at the tip of the pinnule with a single sorus. These fertile pinnules have a 

 peculiar rigid aspect, and this, with their sharp triangular form and their 

 oblique insertion, distinguishes them from the fertile pinnules of Mertensides 

 bidlatus, which, when fully fructified, somewhat resemble them. Seen under 

 a strong lens the sori more commonly present the form given in Plate XXV, 

 Fig. 3 b, but they sometimes appear as given in Fig. 3 c composed of 4 

 sporangia rather remotely placed and grouped around an axis. The form 

 given in Fig. 3b somewhat resembles the dehiscence of Cyathea, but there 

 is no doubt that the sorus is compound. The specimen depicted in Plate 



XXV, Fig. 3, in part, was a very large fragment of what seems to have 

 been a compound pinna of some large frond. Only a portion of the speci- 

 men is figured. It is 25 centimeters long and 1 3 wide. This width and 

 length are much below the former dimensions of the specimen, for much of 

 the length of the ultimate pinnae had been lost from breaking, and a large 

 portion is wanting from both ends of the primary pinna or frond. Plate 



XXVI, Fig. 1 , represents what seems to be a portion from the upper part 

 of the fertile plant. Plate XXV, Figs. 2, 4, and 6, represent portions of 

 the sterile frond, and Fig. 5 gives a somewhat abnormal form, containing 

 on the same pinna both fertile and sterile pinnules. Plate XXV, Fig. 6, 

 gives what appears to be the upper part of a sterile compound pinna where 

 the pinnae are reduced to pinnules. Fig. 4 a gives enlarged leaflets of Fig. 

 4 to show the nervation. The fertile pinnules of this plant resemble some- 

 what Germar's Pecojtteris tnmcata, now considered as an Asterocarpus. Our 

 plant is, of all previously described plants, nearest to Heer's Asterocarnus 

 Meriani, found in the Keuper of Switzerland. It differs from this plant 

 in the stouter midrib of the sterile and fertile pinnules, in the acute fertile 

 pinnules, in the larger sori, which are placed on the margin of the pinnules 

 and not within the laminae, as in Heer's plant, and in the number of the 

 sporangia, which are often five, while Heer's plant contains only four, and 

 also in the much greater size of the rachis of the ultimate pinnae. 



Formation and locality. — The plant is found only at Clover Hill, in strata 

 associated with the main coal seam. 



