318 SYNOPSIS OF THE VERTEBRATE FAUNA OF THE RUERCO SERIES. 



produced farther posteriorly than the external face, which is vertical. Head depressed, 

 convex, and without angles. Cuboid with a small external distal facet. 



This genus is intermediate in character of teeth between Conor3'ctes and Mio- 

 ela^nus. The molai-s are those of the former as to the internal portion of the crown. 

 The external cusps are moi-e those of MiocijBiius, and there is but one external cusp 

 of the first premolar, while there are two in Conoryctes. It is in the i-emarkable 

 table-like form of the interior part of the crown and the hoof-like production of the 

 internal angle, that Onychodectes differs from Miochenus. 



But one species is known to me. 



Onychodbctics tisonensis sp. nov. 



Two individuals certainly represent this species in my collection, both of which 

 include superior molars, while a third, which includes two mandibular rami, belongs to 

 it. Of the former the typical and most important specimen includes the following 

 parts. Both maxillary bones with the posterior five. molars; the left mandibular 

 ramus with all the alveoli, and the second true molar in place; the glenoid extremity 

 of the scapula; the left ilium; the right astragalus and cuboid. 



It is characteristic of the superior molars that the external cusps have a lenticular 

 section, and not a triangular or a round one as in the species of Mioclajnus and Chri- 

 acus. The external cusp of the first premolar is large and elevated, and has the same 

 fore and aft lenticular section with obtuse euttino^ edges. The internal table of the 

 crown is of parabolic outline and its edges are right angles. The sides ascend per- 

 pendicularly to the alveolar border without the least trace of cingulum or other irreg- 

 ularity. The ci-own has a weak external cingulum, which does not support any 

 cusps. The posterior of the external cusps of the third molar is well developed, and 

 nearly in longitudinal line with the anterior. 



The anterior triangle of the second inferior molar has a broadly rounded external 

 a[)ex, and it is a little elevated above the heel. The latter has two internal marginal 

 cusps, but its summit is so worn that the form of the surface cannot be further deter- 

 mined. N^o cingula. The manner of mastication is such as to wear the crown 

 obliquely from within outwards in conformity with the form of the inner table of the 

 su])erioi- molars. The anterior triangle fits, as usual, between two adjacent superior 

 molars, and the claw-shaped internal border of the superior molar worked, scoop-like 

 across the heel, the inferior molar moving from without inwards. The motion was the 

 same as in Conoryctes. In neither genera do I possess the glenoid surface for the 

 mandibular condyle, but it is highly probable from the evident lateral movement of 

 the lower jaw that neither genus possessed a preglenoid crest as is found in Mioclsenns. 



