234 



PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 



The ribs, so far as they are preserved, are similar to those of H. elon- 

 gatus but are relatively somewhat broader and stouter. 



The two segments of the mesosternum (Plate XLIII, figs. 3, 3", 4, 4) 

 most resemble the second and fifth segments of Mylodon (Owen, '42, PI. 

 IX) to which they closely conform in plan of structure ; the dorsal portion 

 of the more anterior segment is an elongate and narrow plate, broadening 

 and becoming more depressed posteriorly; the ventral portion is corres- 

 pondingly elongate antero-posteriorly. The eight facets for the sternal 

 ribs are as in all the other Santa Cruz Gravigrada in which the sternum 

 is known. The more posterior segment is much broader and the ventral 

 part is much less extended in the fore-and-aft direction. 



MEASUREMENTS. 



Last thoraqic, length of centrum 025 



" " width of anterior face ... .027 

 " " " over transverse pro- 

 cesses 056 



height of neural spine . . . .036 

 " " width of neural spine at 



base 023 



" " width of neural spine at 



tip 022 



First lumbar, length of centrum 027 



" " width of anterior face 030 



" " height of neural spine . . . .038 

 " " width of spine at base ... .023 



" " " " " "tip 023 



Second lumbar, length of centrum 028 



Second lumbar, width of anterior face. . .030 

 " " " over transverse 



processes ?. 100 



" " height of neural spine .. .041 



Third lumbar, length of centrum 027 



" " width of anterior face ... .031 

 " " " over transverse pro- 

 cesses 092 



" " height of neural spine ... .036 



Fourth lumbar, length of centrum 025 



" width of anterior face. . .033 



" " " " posterior face. .037 



" height of neural spine .. .031 



" " width of spine at tip. . . .023 



The bones of the fore-limb closely resemble those of H. elongatus but 

 are somewhat longer and decidedly heavier. The scapula differs in a 

 number of particulars, having a more sinuous coracoid border and broader 

 prescapular fossa ; the glenoid cavity is more deeply concave and the 

 spine bears a more distinct metacromion. 



Of the humerus, somewhat less than the distal half is preserved; in 

 the trochlea the articular surface is continuous, as is usual throughout the 

 order, and yet the groove between the radial and ulnar facets is con- 

 siderably deeper than in H. elongatus and the latter has a shorter prox- 

 imo-distal diameter, being reflected less upon the dorsal face of the bone ; 



i 



