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(11). On the Shoulder Girdle of Cynognathus. By R. BKOOM, D.Sc. 



x 



In 1895 Seeley described under the name Cynognathus cratero- 

 uotits the magnificent skeleton which now adorns the British 

 Museum. Though the limbs are missing the skull and vertebral 

 column are well preserved, and the resemblance of the skeleton to 

 that of a large carnivorous mammal is so striking as to constantly 

 force on the attention the question as to whether it may not belong 

 to the group from which the mammals sprang. To those of us who 

 believe that the resemblance is not merely superficial, but denotes 

 a close relationship, it seems important that every detail in the 

 organisation of the group should be known as thoroughly as 

 possible. 



Though the limbs are unknown in Cynognathus, Seeley has thrown 

 considerable light on them from specimens of other Cynodonts, 

 especially Microgomphodon, and I have been able to add a few more 

 facts in connection with Diademedon and ^lurosuchus. Still, there 

 are some points on which nothing is known, and others where our 

 knowledge is very imperfect. 



Some months ago I obtained near Burghersdorp on the farm Vaal- 

 bank some imperfect remains of a skeleton of a species of Cynog- 

 nathus. The remains consist of a large part of the vertebral column 

 with most of the shoulder girdle and pelvis and parts of both upper 

 and lower limbs. The only fragments of the skull are very imper- 

 fect, but it is probable that they belong to Cynognathus crateronotus 

 or an allied species, and the scapula agrees very closely with that 

 of the London type. The specimen, though imperfect, is of the 

 greatest value, in that for the first time we obtain precise knowledge 

 of the structure of the shoulder girdle in a Cynodont reptile. 



The scapula is already well known from Seeley's specimen ; the 

 only point about which there remained any doubt being the lower 

 end. In both the scapulas of the type there is a distinct acromion 

 process. In that of the right side the bone is seen to be a little 

 narrowed below the process and before expanding to meet the precora- 

 coid. In the case of the left scapula, the anterior margin of the bone 

 has been restored and made considerably too large and thick. In 



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