part 2] GEOLOGICAL HISTOBT OF THE GENUS STRATIOTES. 125 



Tracey lignite, which may possibly therefore be rather older than 

 has been generally thought. 



I have been enabled to do this work by a grant from, the 

 Department of Scientific & Industrial Research, which I hold as 

 a Research Student under Mrs. E. M. Reid. 



But for the kindness of many persons, both in this country and 

 abroad, who gave or lent specimens of Stratiotes, it would have 

 been impossible to conduct an investigation such as this, which 

 involves the study of material from diverse localities. In this 

 connexion I would mention Dr. Knud Jessen (Denmark), 

 M. Gustave F. Dollfus (France), Dr. W. Gothan, Dr. P. Menzel, 

 and Dr. J. Zinndorf (Germany), and Mrs. Reid, Prof. J. E. Marr, 

 and Mr. G. W. Colenutt in this country. 



It had long been realized hy the late Clement Reid, F.R.S., 

 that the whole question of Stratiotes was in great need of re- 

 investigation, and it was his intention to study the subject 

 thoroughly. With this end in view, he had brought together 

 many examples, including a great number of specimens of S. aloicles, 

 recent and fossil, from English and German localities, S. Jcalten- 

 nordlieimensis from various localities in Germany, S. websteri 

 from the Isle of Wight, and many specimens of S. headonensis ; 

 also an extensive literature on the subject. 



All this material has been placed at my disposal hy Mrs. Reid. 

 For this, and for her many other kindnesses, which include most 

 valuable help and criticism, I thank her very warmly. It has 

 heen a great privilege to have been entrusted with the carrying 

 out of this work. 



VIII. Description of Species. 



1. Stratiotes headonensis, sp. nov. (PI. V, figs. 1-3, 24-26 

 & PL VI, fig. 23.) 



1851. Carpolithes thalictroides Brongniart (Wright 11). 



1856. G. thalictroides Brongniart (Forbes 15). 



1862. Folliculites thalictroides Brongniart (Bristow 21). 



1887. C. (F.) ivebsteri Brongniart (Starkie Gardner 29). 



1888. C. thalictroides Brongniart (Gardner, Keeping &Monckton 30). 



Seed oblong, ovate or tending to he trigonal or quadrangular, 

 hooked at the base, flattened ; keel usually very broad and flat, 

 frequently from a third to half the breadth of the seed, not 

 continued round the base, not merging gradually into the collar ; 

 collar small, pronounced, warty ; testa thick, woody, ornamented 

 with longitudinal ridges which are more or less continuous from 

 neck to apex, where they gradually die out; surface of keel usually 

 without ridges ; external pitting of surface fairly coarse and 

 uniform on body and keel. Micro pyle basal or sub basal, slightly 

 oblique ; hilum hasilateral, often marked by an angle at the 

 margin ; dorsal wall thickest towards the base ; raphe marginal 



