160 ME. A. C. HADDON ON THE EXTINCT 



plastra of small size, and a portion of a much larger one. In all the thinness of the 

 bones is very remarkable. 



Vertebral column. — "We have 74 specimens of cervical vertebras, all being well repre- 

 sented except the 1st, of which no example is known. The 6th does not present the 

 foramen noticed by Giinther {lot: tit. p. 57 ; also Ann. & Mag. N. H. 1873, xi. p. 397) ; ' 

 for out of our 13 specimens of this bone only one has a perforation, which is very small, 

 and might even be accidental. The foramen apparently only occasionally is present, and 

 that only in old animals. 



There are several examples of dorsal and caudal vertebras. 



In the majority of cases it has been impossible to distinguish between the slender 

 and the stout varieties. There is a certain amount of variation in the size of the haemal 

 spine, in the thickness of the centrum, &c. 



Length of centrum 



Depth of centrum in the middle .... 

 Horizontal width of middle of centrum 



Width of anterior condyle 



Width of anterior glenoid cavity .... 



Width of posterior condyle 



Width of posterior glenoid 



Distance of outer margins of anterior 



zygapophyses 16 broken 25 20 29 .. 25 30 



Distance of outer margins of posterior 



zygapophyses 20 23 23 19 broken . . 2S 37 



Shoulder-girdle. — There is great uniformity about these bones, the chief degrees of 

 variation being in the form of the transverse section of the scapula near the glenoid fossa. 

 The general form of the precoracoid ("acromion") reminds one of the same bone in 

 T. triserrata, in being laterally compressed proximally, and vertically compressed distally. 

 In his monograph, Dr. Giinther remarks (p. 59), " It must be mentioned that there 

 are in the collection a right and a left scapula, evidently belonging to the same individual, 

 which differ remarkably from all the others in not having the coracoid ankylosed, although 

 the individual appears to have been fully adult, and in having the body of the scapula 

 proper uniformly compressed. It is difficult to account for this apparently individual 

 aberration." Now, out of the 85 scapulae in our collection, there are 32 in which the 

 coracoid is ankylosed to the remainder of the shoulder-girdle, leaving 53 in which that 

 bone is distinct ; of these, 23 are of larger size than the smallest of the ankylosed bones, 

 several being considerably so. Thus it seems to be a characteristic of this species for 

 the coracoid to be very irregular in its ankylosis with the coraco-scapula. 



It is interesting to note that in one example there is a tendency towards the formation 



