420 iJ. W. Berry — Potamogeton from Upper Cretaceous. 



Art. XXVIII. — A Potamogeton from the Upper Greta* 

 ceous; by Edwaed W. Beery. 



Since in some eases it is not practicable to determine 

 fossil foliar remains conclusively, those cases in which 

 this is possible merit emphasis lest they be buried in large 

 systematic works on paleobotany and thus run the risk 

 of escaping the attention of botanists and those authors 

 who speculate on the existing distribution of plants while 

 ignoring that of their ancestors. 



The conclusive characters of the Potamogeton 

 described in the present note merit calling attention to 

 it in advance of my account of the associated flora, which 

 may be long delayed. Relics of aquatic vegetation are 

 generally much less durable than those of terrestrial 

 forms and hence there is a relative paucity of such types 

 in the geological record. Circumstantial e\nLdence, as for 

 example the delicate dental armature of Trachodon and 

 other herbivorous dinosaurs, seemingly demands a soft 

 plant food such as is furnished by aquatic plants, but the 

 paleobotanist has but little to offer to the zoologist in 

 answer to questions of this sort. 



There is then a special interest attaching to aquatic 

 fossil plants. In the very large American Upper Creta- 

 ceous floras the bulk of the fossils represent conifers 

 and dicotyledonous leaves. Monocotyledons, aside from 

 palms, are exceedingly rare, and this is usually considered 

 as due to the imperfection of the record rather than as an 

 actual portrayal of the true facts. 



That the secondarily acquired aquatic adaptation in the 

 angiosperms had already progressed a considerable 

 distance before the close of the Upper Cretaceous is 

 indicated by a number of rare forms found in deposits of 

 estuary or lagoonal muds toward the upper part of the 

 Mississippi embayment in Ripley time. These comprise 

 the species of Potamogeton described below: A second 

 species of Potamogeton, as yet undescribed since it may 

 represent the submerged leaves of the former: a form 

 referred to the genus Alismaphyllum: another that 

 suggests the existing genus Hydrilla of the family 

 Hydrocharitaceae : and a fifth of unknown identity, which 

 is believed to have had the form and habit of Vallisneria, 

 and to belong also to the Hydrocharitaceae. 



The new species of Potamogeton may be described as 

 follows : 



