Structure of the Fossil Saurians. 289 



Cuvier, with which he also classes his Gavial de Boll, the 

 remains of a totally different Saurian, which I have considered 

 as the Macrospondylus. Of the Aeolodon there hitherto exists 

 but one species A. priscus, from which the above description 

 is taken. 



2. Rhacheosau'rus. 



The remains which enabled me to establish the Rhacheo- 

 saurus I discovered in the year 1829. They have been 

 fully described by me, and figured of the size of nature, 

 in the Acts of the Royal Leopold and Caroline Academy of 

 Naturalists, They are incomplete as regards the head, the 

 neck, the apparatus of the breast, the forelimbs, and the tail. 

 The vertebral column exhibits in its posterior surfaces the 

 concave form, and is only half as long as that of the Ae61odon. 

 The relation of the diameter to the length is different in the 

 vertebral column of both animals. Towards the pelvis, the 

 vertebrae become the longest; while both the Crocodile and 

 Monitor differ in this particular. The spinous processes are 

 extremely broad ; the highest are placed before and behind 

 the pelvis, and also on the longest vertebrae. The spinous 

 processes of the caudal vertebrae differ from those of the 

 dorsal vertebrae, and from the spinous processes of all 

 Saurians hitherto known, in this particular, that a second 

 spinous process rises before it, which is smaller, thin, and 

 pointed like an actual spine. A like structure only occurs 

 in fishes. The chevron process is also found in the ver- 

 tebrae of the tail, and, like the other processes in general 

 is most similar to the analogous structure in the Croco- 

 dile. This animal, it is probable, possessed no lumbar 

 vertebrae. The ribs are attached by their head to an in- 

 equality of the vertebrae, and are also articulated to the trans- 

 verse processes. The last ribs were probably connected only 

 by their head with the vertebrae; in which particular they 

 more resemble the ribs of the Lacertae. The section of the 

 ribs is nearly round. The abdomen of the animal also 

 possessed its ribs, which formed a continuation with those 

 of the back. In the middle of the belly, they joined in a 

 point, which was probably directed forwards. The pelvis 

 rather resembles that of the Crocodile than of the Monitor ; 

 its bones, however, are much shorter, stronger, and broader. 

 The transverse processes of the vertebrae of the pelvis are 

 much longer than in the Crocodiles. The femur appears to 

 have been more bent than in the Aeolodon, though not 

 so much so as in the crocodile. The length of the tibia is 

 less than the third part of the length of the femur. The 

 toes are very long compared with the leg. There are four, 



