292 PALEONTOLOGY. 



found only in the streams, rivers, and great fresh-water lakes 

 of the warmer regions of the earth. 



Very fine specimens of the fossil species of this family, 

 nine in number, have been found in the lacustrine eocene sand 

 of Hordwell, the fresh- water limestone of the Isle of "Wight, 

 the clay of Sheppey, and the sands of Bracklesham. Eor an 

 admirable description and exquisite figures of these Trionyces, 

 the student is referred to the monograph by Professors Bell 

 and Owen.* The Hordwell specimens are in the cabinet of 

 the Marchioness of Hastings. The annexed figures are from 

 specimens obtained from the fresh-water limestone of the 



of Wight.f 



FIG. 197. Sternal Plate of Fresh-water Turtle, from Binstead. 



(One-third linear the natural size.) 

 The outline, a, represents the corresponding portion of the plastron. 



4th Family. The CHELONID^, or marine turtles, have 

 the carapace cordiform and depressed like an elliptical arch, 



* Palscontograpliical Society. " 

 f Dr. Mnntcll's Isle of Wight. 



