Unionidm of the Country of the Iguanodon. 403 



trees, from ten to twenty five feet in length, and from two to 

 four or five feet in circumference, were lying prostrate half im- 

 bedded in the sand, and partially encrusted with fuci, and flustrae, 

 and corallines. A microscopical examination demonstrates that 

 these trees belong to the ConifercB; and this inference is corrob- 

 orated by the discovery of several small cones belonging to three 

 or four species of Finns or Abies. Here then we have the re- 

 mains of a petrified pine forest, which once grew in the country 

 of the Iguanodon ; for the bones of that reptile, and of others 

 equally gigantic, are associated in considerable numbers with the 

 fossil trees. The trunks of these trees are converted into a com- 

 pact calcareous stone of an ebony color, often permeated by py- 

 rites, and having the bark in the state of friable lignite ; but this 

 investment is soon washed away, and the exposed stems are left 

 bare, their surface displacing the ligneous structure with knots, 

 and remains of branches. I observed one portion of a trunk 

 which indicated a tree of considerable magnitude — not less than 

 ten or eleven feet in circumference. 



From among the remains above described, I obtained several 

 examples of a large bivalve, having the external configuration of 

 an Unio ; but all the specimens were closed shells, filled and 

 firmly cemented together by compact stone, and the structure of 

 the hinge was altogether concealed. With considerable difficulty 

 I have succeeded in separating the valves of one pair of shells, 

 and have developed the characters of the hinge most satisfacto- 

 rily, by which, the nature of these bivalves is clearly demonstra- 

 ted. These shells are in a remarkably fine state of preservation. 

 The ligament remains entire ; even the color of the original is 

 not entirely obliterated ; and traces of the thick internal pearly 

 or nacreous coat of the shell remain. The following descrip- 

 tion embraces the essential character of these inhabitants of the 

 lakes and rivers of the country of the Iguanodon ; the specific 

 name is intended to designate their geological habitat — the Weal- 

 den formatioti. 



Unio Valdensis, (G. A. M.) The form of this species is ovate, 

 the anterior extremity more rounded than the posterior, which 

 is somewhat narrowed by the ligamental slope. Length (antero- 

 posterior diameter) five inches ; height (from summit to base) 

 three inches ; diameter (depth or greatest thickness of the united 

 valves) two inches. Equivalves subequilateral ; the posterior 



