94 REVISION OF THE PELYCOSAURIA. 



The ischium has lost a small portion of the distal end. The upper edge slants 

 down and back and the lower edge slowly rises so the bone ends in a blunt point. 



Th.Q/emiir is rather more elongate and slender than in Diopeiis. The posterior 

 depression of the proximal end is deep and the inner edge is developed more as a 

 tuberosity tlian a ridge. The shaft is rounded at the middle with a light riigose line 

 on the posterior face. The condyles lie on the posterior face looking backward more 

 than downward ; the)- are distinct, but not so clearly marked as in Dimetrodon. 



The tibia is about three-fourths as long as the fennir, the proximal end is 

 enlarged and the shaft is bent. The proximal face is divided by a groove as in Dime- 

 trodon^ but the division is not nearly so prominent nor is there a cnemial crest. The 

 distal end is broken. 



Th.^ fibula is a simple flattened shaft curved like the tibia. The distal end ter- 

 minates in two facets set at a large angle to each other. 



The posterior foot : The tarsus of the left foot and the proximal ends of four 

 metacarpals. The careful cleaning of the specimen shows that the element described 

 by Cope as the fifth metatarsal is really an element of the tarsus. The tarsus is com- 

 plete and the bones lie in their proper places, but man}' of them have been slightly 

 moved in their places so that they no longer articulate accurately. There are eight 

 elements in the tarsus. 



The Jibidare (calcaneum) is twisted until it lies nearly at right angles to the 

 normal position and the faces normally applied to the tibiale are presented to the 

 front. The main portion of the bone is flat and disk-like. On the inner edge are the 

 faces for the tibiale; above the inner edge is beveled by a face for the fibula and 

 distally there is a face for the intermedium (cuboid). 



The tibiale (astragalus) is roughly L-shaped, the two points on the inner side are 

 applied to the fibulare and the outer part tenninates in a thickened roughened 

 surface. This lower part leaves the vertical portion more gentl)- than in some others. 

 The two facets of the inner side applied to the two facets of the fibulare leave between 

 them a foramen through which a blood-\-essel penetrated the foot. Below the tibiale 

 articulated with the centrale i (navicular), and by its lateral internal corner with the 

 intermedium + (cuboid). 



There are two large bones in the second row of the tarsus, the centrale i and 

 the intermedium +. The former is rather rectangular, longer than high and articu- 

 lates with the tibiale above, tarsals i and 2 below and the intermedium ,1- below. 



The interinediuni 4- is a large bone evidently compounded of two or more origi- 

 nally distinct elements. It articulates with the tibiale and fibulare above and extends 

 distalh' to support the fourth metatarsal. From its position it seems that it is either 

 the intermedium + centrale 2 + tarsale iv or intermedium + centrale 2 ; in the latter 

 case it would be necessary to assume that the tarsale iv has been lost and there is 

 nothing in the appearance of the foot to warrant such an assumption. The bone is 

 very long vertically and near the middle presents a sharp angle, as if two elements 

 had fused. 



Tarsale i : This articulates by a broad face with the centrale i and sends a 

 strong process laterally from the distal end which widens the end to accommodate a 

 long and narrow facet for the head of the metatarsal 5. 



Tarsale 11 and iii are small elements with large facets for the corresponding 

 metatarsals. From the dorsal side it is evident that tarsale i, 11, and in articulate 

 proximally with the centrale i. On the ventral side tarsale 11 is not visible having 

 been crowded back by the crushing of the foot. 



