224 



Professor Williamson on some 



[Feb. 16, 



the strongest affinities. This difficulty is especially felt when study- 

 ing the large, ill-defined genera, Pecopteris, Neuropteris, and Sphe- 

 nopteris. Three examples may be selected from the latter genus in 

 illustration of the worthlessness of our present classification of these 

 objects. 



In 1837 I figured and described, in the ' Fossil Flora of Great 

 Britain,'* the first discovered examples of the Yorkshire Oolitic genus 

 Tympanophora. Their nature was then wholly problematical ; but in 

 1844 1 I discovered that the Tympanophora racemora was but a 

 sporangial pinnule of the Pecopteris Murrayana of Brongniart, the 

 Splienopteris Murrayana of Phillips. I have now before me another 

 Sphenopteris from the Yorkshire coast, apparently the Splienopteris 

 hymenophylloides (^S. stipata of Phillips), in which the fertile pinnules 

 are also Tympanophorse. Fig. 5a represents the sterile and Fig. 5b 

 the fertile forms of this plant. Brongniart compares this sporan- 

 gial fructification with that of the arborescent Thyrsopteris ; but it 

 may with equal propriety be compared with that of several of the 

 Davallias or Hare's-foot ferns. But a very different form of Sphenopteris 



Fig. 5a. 



Fig. 5b. 



Sterile leaflets of Sphenopteris 

 hymenophylloides. 



Fertile leaflets of Sphenopteris 

 hymenophylloides. 



has just been described by Mr. Eobert Kidson of Stirling, under the 

 name of Sphenopteris tenella of Brongniart, but which latter, he 

 informs me, he now regards as a synonym of Gutbier's Sphenopteris 

 lanceolata, the older name. I am indebted to Mr. Kidson for speci- 

 mens of this plant with the sporangia of the fertile fronds in an 

 exquisite state of preservation. As is so often the case with the spore- 



* Vol. iii. pi. 170. 



t Brongniart's ' Tableau des genres de Vegetaux fossiles,' p. 46. 



