Survey of Wyoming, 1871, p. 359.--_Limnohyus robustus._--Marsh, American Journal Science and Arts, 1872, p. 124. _Specific characters._--Sagittal crest short and thick. Temporal fossæ not very deep. Frontals diverge rapidly. Occipital condyles wide and low; the same is true of the foramen magnum. Meatus auditorius high and deep. Glenoid cavity shallow; no internal process. As compared with _P. Paludosus_, post-glenoid process not so much compressed. Occipital region comparatively higher and not so concave. The occipital condyles are more prominent. The zygomas are lighter. Head larger than _Paludosus_, perhaps not so large as _Vallidens_. Description from (i) a head, complete, but distorted, with complete dentition, upper and lower. (2) A head somewhat crushed, and lacking some portions, with full set of upper molars and canines. (3) A great number of fragmentary specimens of different parts of the body. _Dentition._--In the upper jaw the incisors are arranged in a semi-circle as in _P. paludosus_; they have long fangs and short, conical crowns, with a decided basal ridge, which is very strong in the third. They increase from first to third, which is very large and pointed. The canines have very large and long fangs (longer than the crowns). The crowns are very stout and pointed, constituting formidable weapons. In section they are nearly circular, with a distinct hinder margin and a slight recurve. A rudimentary anterior margin is sometimes present, and of the faces thus marked off, the inner is much smaller and flatter. The general direction is forwards, downwards, and slightly outwards. There is a diastema of about half an inch between the incisors and canines. _Premolars._--The first is very small, about half an inch from the canine, simple and conical, with an obscurely marked basal ridge, and two heavy fangs. Further description of the upper dentition is unnecessary, owing to the complete work of Dr. Leidy upon the subject. The _lower incisors_ are placed in a semi-circular row, and are somewhat procumbent, though hardly as much so as in the tapir. They are much as in _P. paludosus_, but are relatively smaller, and have not such distinct basal ridges; features which indicate a departure from the carnivorous type, and a nearer approach to the herbivorous type. The lateral incisor, though the largest of the series, is not so large nor so pointed as in _P. paludosus_. There is no diastema. The _canines_ are about equal in size to those of the upper jaw, growing from stout fangs and permanent pulps. The margins of the crowns are more decided, and are smooth, leaving a very narrow and flat inner face. A feeble basal ridge. When the jaw was closed, the lower canines passed inside and in front of the upper.