226 



PROCEEDINGS OF THE ACADEMY OF 



[1880. 



caneum shows a prominent process, which is as strongly developed 

 in Proailurus and Procyon, and to a less degree in Cryptoprocta 



and Amphicyon. This process is most con- 

 spicuous in the plantigrade forms, though 

 it is also present in such forms as the tiger. 

 The astragalus of Dinictis is remarkable 

 for its flatness, the intercondylar groove 

 being hardly more than indicated ; the outer 

 condyle is much broader and somewhat 

 higher than the inner and forms nearly a 

 right angle with the very large and slightly 

 concave external fibular surface ; at its pos- 

 terior (or superior) end the trochlea becomes 

 exceedingly narrow and somewhat more 

 deeply grooved ; anteriorly it ends abruptly 

 and is not continued down over the neck, 

 as is the case in Archcelurus and the tiger. 

 The internal face of the astragalus is placed 

 very obliquely and passes into the inner 

 condyle by a gentle curve, quite different 

 from the sharp ridge found in most recent 

 carnivores, but very similar to the shape in 

 Archcelurus. The neck is very short and 

 much less strongly deflected towards the tibial 

 side than is usual in recent forms; the distal 

 end is formed by the large convex head for 

 the navicular, but upon the outer side there is a small, though distinct 

 facet for the cuboid, a connection which rarely occurs in the recent 

 carnivora, the bears and certain mustelines having it, however. Cope's 

 figure of the astragalus of Archcelurus (No. 2, PI. lxxia, fig. 1Gb) 

 seems to indicate its occurrence in that genus, and in all probability it 

 will also be found in the White River species of Cijnodictis, though in 

 the G. geismarianus from the John Day horizon (Cope, No. 2, PI. 

 lxxa, fig. 9) it is not apparent. The facet for the sustentaculum 

 is long and rather narrow, convex in front and concave behind, as it 

 embraces the hinder edge of the sustentaculum ; the external cal- 

 caneal facet is deeply concave from before backwards, and has an un- 

 usually oblique position in accordance with that of the corresponding 

 surface on the calcaneum. The resemblance in the structure of the 

 astragalus between Dinictis and Archcelurus have been mentioned. 



Fig. 4- 

 hind foot 



Dinictis ft Una ; left 



