slender bundles adhering to its surface or only slightly sunk. The endocarp of S. simplex 

 is also much smaller than our fossil; but it shows some approach to the fusiform shape, 

 has the vascular bundles slightly sunk in the endocarp, and the bony endocarp between 

 the bundles swells out slightly. 5. simplex is the nearest living ally of our fossil ; but 

 its endocarp is very small, and only shows a slight approach to the nodose endocarp of 

 markedly fusiform shape so characteristic of 5. noduliferum. With the exception of the 

 few endocarps already described as resembling 5. ramosum and 5. minimum, all our fruits, 

 though variable, seem to belong to the present species. 



Fruits of 5. noduliferum have also been sent to us by Professor Kinkelin, who 

 obtained them from the Pliocene of the Untermainthal. We have not seen the species 

 from Tegelen. 



POTAMOGETONACEAE. 



POTAMOGETON. 



This genus is well represented in the Reuverian beds, no fewer than 10 species 

 having been found. None of these correspond with living British forms; but the genus 

 is so difficult, and there is so much uncertainty in the determination of living forms, 

 that we prefer not to describe our fossils as new on the evidence of endocarps alone. We 

 merely number the species from 1 to 10. It is unfortunate that so little attention is paid to 

 the endocarp in the recent plant, for in Potamogeton it is far more easy to figure and describe 

 accurately than the soft epicarp, which tends to shrink and change greatly in drying. 



All the species of Potamogeton here described seem to be mere variants of the 

 living types. The Pliocene strata have not yet yielded anything resembling the P. tenuU 

 carpus of the Lower Miocene of Bovey Tracey, which has a thin translucent endocarp 

 with granulate surface. Nor has anything allied to the Lower Oligocene (or Upper 

 Eocene) Limnocarpus been found. This latter has only two carpels, and a hard crusta* 

 ceous muchspitted endocarp. 



The figures and descriptions of most of the extinct species of Potamogeton are 

 too imperfect to allow of comparison with our fossils. 



POTAMOGETON Sp. I. 

 PI. II, fig. 1. 



Nuts semi*orbicular truncate below inflated, with small but deep central depress 

 sion, ventral margin nearly straight, dorsal margin semicircular, attachment subsbasal; 

 style apical long directed outwards; keel (not reaching quite to style) sharply crested, 

 with a strong spine near the base; surface of endocarp showing irregular cells elongate 

 radially; endocarp hard and thick. 



Length (including style) 3.5 mm., breadth 2.2 mm. Brunssum. 



This is the largest nut we have found, and its hardness makes it resist compression, 

 so that it is less distorted than the other species. It only occurs at Brunssum. 



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