474 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 



Upper dentition, length 037 Palate, width at p 005 



" " " p4-m* 0165 " " "ml oio 



Upper incisor, width 003 Humerus, distal width 0095 



" " thickness 0035 " width of trochlea 007 



Pi, length 0025 Radius, proximal width 006 



" width 003 Femur, " " 018 



Skull, length, occipital condyle to pre- " distal " 013 



maxillary 072 Tibia, proximal width 015 



Rostrum, width at base 014 " " thickness 012 



" " " anterior end 009 



EOCARDIA EXCAVATA (Ameghino). 



(Plates LXVIII, Fig. 25 ; LXIX, Figs. 3-10.) 



Dicardia excavata Amegh.; Rev. Argent, de Hist. Nat., T. I, 1891, p. 



302. 

 Tricardia gracilis Amegh. ; Ibid. 



The following description is founded upon the types in the Ameghino 

 collection and upon the most complete individual respresentative of the 

 genus which has yet been found. This specimen (No. 15,211), a nearly 

 entire skeleton, was collected by Mr. Hatcher on the Atlantic coast of Pata- 

 gonia, ten miles south of Coy Inlet. 



The average individual of this species is smaller and slighter than E. 

 montana, though connecting variations in regard to size are such that the 

 difference is by no means striking ; the incisors are more slender, but p- is 

 larger, while m 1 has a decidedly smaller posterior process. P A is very 

 variable, as is shown by the difference between the two sides of the same 

 mandible ; the anterior prism is usually, but not always, larger than the pos- 

 terior and has a deep groove on the anterior face, which is sometimes so deep 

 as to produce three well denned external, vertical crests (Tricardia]. In 

 No. 15,21 1 this groove is much better denned on the left side than on the 

 right, and it would be no great exaggeration to say that in this individual 

 the right half of the mandible belonged to E. excavata and the left to 

 Tricardia gracilis. 



The skull is not very completely known in this species, for in the nearly 

 entire specimen (No. 15,211) almost the whole top of the skull has been 

 weathered away and what remains has been considerably distorted by 

 pressure. It is plain, however, that the skull is relatively narrower and 

 more elongate than in E. montana, that the zygomatic arch, especially 



