^20 ON CHLAMTDOPHORFS TRUNOATUS. [Feb. 19, 



B'-fore leaving the salivary glands, it may be mentioned that in 

 the Sloth the socia parotidis (text-fig. 19, s.p.^L) is very large and 

 of unusually definite shape. It is a long pear-shaped body situated 

 at some distance dorsal to Stensen's duct, into which it opens by 

 a single duct 9 ram. in length, that emerges from its anterior 



pointed end. -,t ,-,, i • i- c ^i 



TJie Heart.— 1 have nothing to add to Hyvtl's description ot the 

 heart, and I find in two specimens that the great vessels rise from 

 the aortic arch in a manner similar to that previously recorded ; but 

 there is a slight peculiarity in the conformation of the arch itself 

 that merits "a brief description, not so much for its intrinsic 

 importance in Ohlamydopliorus, as because a similar though 

 exaggerated modification forms a very striking feature in the aorta 



Text-fig. 20. 



Heart of Tbree-toed Slotli {Bradypns tridactylus). 



of the Sloth. The peculiarity in question consists of a marked 

 depression of the transverse part of the arch towards the ventral 

 surface. The ascending aorta is short, and at the commencement 

 of the transverse part bends sharply forward towards the ventral 

 surface of the heart, and then curves round towards the dorsum 

 compressed between the base of the heart and the trachea. The 

 convexity of the arch thus lies in the transverse plane of the 

 heart, instead of approximately in its longitudinal plane as is usually 

 the case. In two other Edentates (Tamandua and Myrmecophaga) 

 that I have examined, the arch lies in the longitudinal plane as 

 usual, but in the Sloth {Bmdypus tridactylus) there is a ventral de- 

 pression of the aortic arch of a most marked character (text-fig. 20). 

 In both cases, the depression appears to be due to the pressure of 



