SYNOPSIS OF THE VERTEBRATE FAUNA OF THE PUERCO SERIES. 345 



distance on the anterior face, to correspond witli the fossa of the neck of the astra- 

 gahis. The astragahis is somewhat depressed, and is quite oblique to the vertical 

 phme. The neck is of moderate length, and is depressed, and the navicular facet 

 slopes at an angle of forty-five degrees when the astragalus rests bn a plane surface. 

 The long axis of the trochlea slopes at an angle of thirty degi-ees to the long axis 

 of the entire bone, outwards and forwards. The posterioi- foi'amen is completely 

 enclosed. The malleolar face is oblique, the fibular vertical. The articular surface 

 of the trochlea is continued in an excavation of the neck to its middle, and is ter- 

 minated by an acute recurved boundary. This indicates a foot frequently held at 

 right angles to the leg, and a plantigrade walk. The obliquity of the astragalus, 

 which fits the tibia perfectly, means that the hind legs diverged to the leet in a very 

 obvious manner. If the calcaneum is placed on a plane surface this divergence is 

 still greatei-, since the calcaneum is obliquely related to the astragalus, as the latter 

 is to the tibia. The animal may have, however, walked on the external edge of the 

 foot. The sustentaculum is not very large as compared with the cuboid facet. The 

 latter is trapezoid in outline, the four sides all unequal, being related as to length in 

 the following order, beginning with the longest — inferior, su])enor external, superior 

 internal, internal. When the astragalar facets are held in a horizontal plane, the long 

 axis of this face is horizontal. In this position, the inferior sui-face of the calcaneum 

 is a narrow obtuse ridge, bounded on the external side by a wide deep gutki'. This 

 is bounded above by an angular border of a nai'row superior-external face, which 

 widens posteriorly. The superior surface is an obtuse I'idge. The internal sui-face is 

 undivided by groove or ridge and slopes outward below. The inferior ridge termi- 

 nates in an acumination at the inferior border of the cuboid facet. In front of the 

 astragalar facets, the superior face of the calcaneum has three longitudinal fossa) 

 separated by low ridges. The; internal, which is in front of the sustentaeular, is twice 

 as large as any of the others. A transverse section through the middle of the cuboid 

 bone is irregularly triangular. The external ftxce is smooth. On the inferior face the 

 large tuberosity is flattened, and is subquadrate in outline. It is separated from the 

 edge of the metatarsal facet by a gi'oove which is, however, closed at both ends, indi- 

 cating that it has not a pulley-like function for the usual tendon. On the intt lo- 

 superior face we have j)roximally a smooth band I'nr the navicular, and about the 

 middle, an oval facet transversely j)laccd f'oi' the ectocuneVfoiin. The cuboid and 

 navicular do not tluii present in different directions as they do in Oxyjena, but in the 

 same direction, as in Mesonyx.* The ectocuneiform is deeper than long, and longer 



* Scoll, On New anil Little Known Crcodonts, Jour. Phil. Acad., 1886, p. 103. 



