34 J. W. HULKE ON THE VERTEBRiE OF OENITHOPSIS. 



figure; the under surface is only very slightly flattened. The 

 lateral opening and the chamber are smaller. I am inclined to 

 regard this centrum as having occupied a position in the vertebral 

 column posterior to the two just described. The form of the arti- 

 culations and the superadded zygosphenal arrangement are calcu- 

 lated to greatly limit the mobility of the vertebrae on one another 

 in this region. With respect to the orifice of the large-sided cham- 

 bers in these vertebras, Prof. Seeley, finding them paralleled in 

 birds and Pterosauria, regarded them as pneumatic. Prof. Owen, 

 on the other hand, thinks that they were more probably filled 

 with chondrine ; and in a recent discussion he supported this view 

 by a reference to the vertebrae of fish. On this hypothesis it is not 

 apparent to me why the chambers should attain their maximum de- 

 velopment in the fore part of the trunk, be absent from the neck, 

 and lessen towards the loins. Why should such a connective sub- 

 stance as chondrine be thus limited in its skeletal distribution? 

 Eather does not such limitation strengthen the opinion of their 

 being air-chambers? In Birds, particularly those endowed with 

 great powers of flight, e. g. Albatross, the pneumatic opening in the 

 side of the vertebral centrum is largest precisely in the same situa- 

 tion as in Eucamerotus ; it is also wanting in the neck, and it rapidly 

 lessens towards the sacrum. In noticing this parallel I would, 

 however, not be understood to afiirm that Eucamerotus was capable 

 of flight. 



Tail. — All the vertebrae yet discovered which I can confidently 

 refer to the animal belong to the neck and trunk. I know of 

 none which bear chevron facets or other marks whereby to assign 

 them to the tail, a circumstance which is not without significance 

 when we consider the large number of vertebrae in most reptilian tails. 

 May its caudal vertebrae be, like those described in certain of the new 

 American forms, unchambered and relatively solid ? In the same 

 Wealden beds which have yielded these cervical and dorsal vertebrae 

 caudal vertebrae not unfrequently occur. Of these, the most common 

 are those laterally flattened forms which are correctly assigned to 

 Iguanodon, JN"ext in frequency are two types which have usually 

 been given to Ceteosauri. Of these, one I have good reason to place in 

 the tail of Iguanodon immediately behind the spot where the trans- 

 verse process disappears. The other, which often attains much 

 larger dimensions than in Iguanodon, is also relatively shorter and 

 of coarser texture. May these belong to Eucamerotus ? Not long 

 since I should have rejected this conjecture as unworthy of attention; 

 but the late Colorado discoveries show that it would not be safe to 

 do so. 



