222 DINOSAURS OF NORTH AMERICA. 



is reversed, the ridged face of the crown being on the inside. This 

 arrangement greatly increased the cutting power of the jaws. The 

 food was probably soft vegetation. 



THE BRAIN. 



The brain of Claosaurus was very small, its size in proportion to the 

 skull being represented -in PI. LXXVI, fig. 2, which also shows the 

 exact position of the brain in the cranium. A cast of the brain cavity 

 is shown in PI. LXXVII, fig. 3, one-fourth natural size. The brain as 

 a whole was considerably elongated, especially the posterior half. The 

 olfactory lobes were well developed, and not separated by an osseous 

 septum. The cerebral hemispheres were comparatively large, forming 

 nearly or quite half the entire brain. The optic lobes were narrow, 

 but considerably elevated. The cerebellum was rather small, and also 

 much compressed. The medulla was of good size, and nearly circular 

 in transverse outline. ' The pituitary body was quite large. The inter- 

 pretation of some of the more minute features of the brain is a matter 

 of difficulty, and will be more fully discussed elsewhere. 



the vertebim:. 



The main characters of the vertebral column of Claosaurus are well 

 shown in the restoration (PI. LXXIV). There are thirty vertebrse 

 between the skull and sacrum, nine in the sacrum, and about sixty in 

 the tail. The whole vertebral column was found in position except the 

 terminal caudals, which are here represented in outline. The cervical 

 vertebra? are strongly opisthocceliau, and the first eleven have short 

 ribs. The dorsals are also opisthocceliau. There are no true lumbar 

 vertebne, as the last of those in front of the sacrum support free ribs. 

 The anterior caudals are opisthocceliau. The first and second have no 

 chevrons. Behind these the chevron bones are very long, indicating a 

 powerful, compressed tail, well adapted for swimming. 



In the median dorsal region, between the ribs and the neural spines, 

 are numerous rod-like ossilied tendons, which increase in number in the 

 sacral region and along the base of the tail, and then gradually dimin- 

 ish in number and size, ending at about the thirty -fifth caudal. These 

 ossilied tendons are well shown in the restoration, and are of much 

 interest. They are not unlike those in Iguanodou described by Dollo, 

 but as a rule are more elongate, and appear to lack the definite arrange- 

 ment in rhomboidal figures observed in that genus. 



THE FORE AND HIND LIMBS. 



The fore limbs are unusually small in comparison with the posterior, 

 and the relative size of the two is shown on PI. LXXII1. The scapular 

 arch presents many points of interest. The scapula is large, and so 

 much curved that its shaft is nearly at right angles to the articular 

 faces of its lower extremity (PI. LXXIII, fig. 1, s). On the anterior 



