16 O. C. Marsh on the Remains of a new Enaliosaurian. 



present in the portion first examined. Part of the nitrogen may 

 have been derived from ammonia, which is sometimes intro- 

 duced into fossils bj the infiltrating waters. A want of suflSi- 

 cient material prevented fuller investigations of the organic ele- 

 ments in these remains. 



The fossil bones hitherto- analyzed appear to have been all 

 from the more recent formations ; the present analysis, however, 

 of a Palaeozoic fossil does not differ materially in most respects 

 from the results previously obtained. 



Yale College, April 16th, 1862. 



EXPLANATION OF THE PLATES. 



PLATE L 

 VertehrcB of the Eosaurtts Acadianut (natural size). 

 Figure 1. Oblique lateral view of the vertebrae, with the posterior artic- 

 ular surfaces above, 

 a. Pits for the articulation of the neurapophyses. 

 6. Rudimentary transverse process on the right lateral surface 



c. Notch, or depression, in the posterior margin of the centrum. 

 Figure 2. Oblique view of the vertebrae, with the anterior articular sur- 

 faces in front. 



a, a'. Pits for the articulation of the neurapophyses. 



b. Rudimentary transverse process on left lateral surface. 

 b'. Ditto on right lateral surface. 



PLATE IL 

 Vertebra of Eosaurui (natural size), with magnified sectiont. 

 Figure 1. Posterior view of the more perfect vertebra. 



a. Pits for articulation of neurapophyses. 



b. Rudimentary transverse process on left lateral surface. 

 b'. Ditto on right lateral surface. 



c. Notch, or depression, in the margin of the centrum. 



Figure 2. Transverse section of the same vertebra, showing the deep 

 concavities of the articular terminal facets, and the rudi- 

 mentary processes at b and b'. 



Figure 3. Longitudinal microscopic section, from near the 1 

 of the centrum, showin; " ' ' ' 



Figure 4. View of the reticulated osseous texture on the lateral surface 

 of the centrum. (Magnified five diameters.) 



Figure 5. Transverse microscopic section, from near the articular sur- 

 face of the centrum. (Magnified 350 diameters.) 



