O. C. Marsh on the Remains of a 



a casual examination of the vertebrae, expressed tbe opinion that 

 the notch and elevation were organic, rather than accidental ; and 

 as such were indicative of an inferiority of structure, which 

 would place the genus of reptiles to which the remains belong 

 somewhat lower than the Ichthyosauri In a recent letter to 

 Prof. Silliman, Jr., on the subject, he writes as follows: 



" Mr. Marsh has shown me to-day two vertebrae from the Coal Forma- 

 tion of the Joggins, which have excited ray interest in the highest degree. 

 I have never seen in the body of a vertebra such characters combined, 

 as are here exhibited. At first sight they might be mistaken for ordi- 

 rary Ichthyosaurus vertebrae ; but a closer examination soon shows a 

 singular notch in the body of the vertebra itself such as I have never 

 seen in Reptiles, though this character is common in Fishes. We have 

 here undoubtedly a nearer approximation to a synthesis between Fish and 

 Reptile than has yet been seen. * * * * The discovery of the 

 Ichthyosauri was not more important than that of these vertebrae ; 

 * * * I do not believe that there is a vertebra known thus far, in 

 which are combined features of so many vertebrae, in which these fea- 

 tures appear separately as characteristic of their type." 



At the time Prof. Agassiz saw these remains, thej were only 

 partially separated from the shale in which they had been im- 

 bedded, and consequently his examination could not be perfectly 

 satisfactory. Since then, the matrix has been carefully removed, 

 and an opportunity afforded for comparing the other similar 

 parts of both vertebras. This comparison, however, shows no 

 corresponding notch or elevation at the opposite points of the 

 same centrum; and none whatever on the other vertebra, where 

 such should exist if these peculiarities were organic. 



Prof. Jeffries Wyman, to whom the writer had previously 

 submitted the vertebrae, and to whose kindness he is indebted 

 valuable suggestions in regard to them, considers 

 purely accidental ; and a result of the same fracture 



lich has displaced the articular pits of the superior arch. It 

 is also the opinion of this eminent anatomist that the notch would 

 not be sufficiently important, if it were organic, to affect at all 

 the Enahosaurian character of the remains. 



A microscopic examination of the osseous structure of these 

 vertebrae of the Eosaurus exhibits well-marked Eeptilian char- 

 acters. The Haversian canals are few in number, but large in 

 size, as is usual in this class. The lacunae, although somewhat 

 irregular in shape, are much elongated, and show very little re- 

 semblance to the quadrate or stellate form of tbe bone cells in 

 fishes. They are frequently arranged concentrically around the 

 Haversian canals, as represented in Plate II. figure 3, and their 

 walls are almost invariably well defined. The canaliculi, as in 

 the Ichthyosaurm and Plesiosaurus, are not numerous, but appear 

 to be finer than those in most saurians. They do not taper off 



S par" 



