ny6 



CLASS REPTILIA. 



though it is probable that the humerus was relatively longer. Teeth 

 from the Kimeridgian of Boulogne, upon the evidence of which the 

 genus Neosodon was founded, but which were subsequently identified 

 with American forms described as Caulodon, are probably referable 

 to the same species. Small vertebrae from the Kimeridge Clay of 

 Swindon, upon which the genus Bothriospondylus was established, 

 may perhaps be referable to a very young individual of Pelorosaurus 

 humerocristatus ; while a comparatively small humerus from the 

 same deposits, originally described under the preoccupied name of 

 Ischyrosaurus, may indicate a smaller species of the same genus. 

 Finally, of the Kimeridgian remains described as Gigantosaurus, 

 while some may be referable to P. humerocristatus, a sacral vertebra 

 may belong to the smaller P. Manseli above mentioned. 



The following table gives the dimensions of some of the bones of certain 

 of the above-mentioned forms, together with those of others noticed below 

 under the head of the Cetiosauridce : — 





1 



g 



1 



<-> 



si 



5 



8.«Sts 

 S C & 



* a s 



^8« 



8 



8 



1 



8 



ill 



r 

 45 



t<> 



8 

 8 



8 



Length of scapula . 



6o 









54 





ii humerus . 





5 o? 



54 



57 





36 



5i.5 



24 



it ischium . 





40 





35-5 



27 



30-5 



39? 





ti femur 



74 



70? 









46 



64 





Width of dorsal centrum . 





13 







8.5 







6 



it lumbar n 





14 





11.51 









7 



ii caudal n 





12 











?IO 



7 



Family Diplodocid^e. — The genus Difilodocus, from the Upper 

 Jurassic of North America, is typically represented by a species of 

 smaller size than many of the preceding forms, and is regarded by 

 Professor Marsh as the type of a family. It was originally con- 

 sidered that the external nares were single, and situated at the top 

 of the skull between the orbits (fig. 1076) ; but it now appears that 

 they really formed long narrow slits between the premaxillae, nasals, 



1 Caudal vertebrae of a larger individual are nearly equal in size to those of 

 Brontosaurus. 



