A species of large mud-fishes related to the modern _Amia calva_. The vertebræ are all much wider than they are high. The articular cones have their bottoms considerably above the centre, and are minutely perforate for the notochord. The centrum is transversely curved from side to side, and has the convexity directed forwards; it is truncate below, making the infero-lateral angles quite prominent in the anterior dorsal region; in the posterior there are two fossæ. The diapophyses are large, but almost sessile, and take their origin above the centre, on the same line as the bottom of the articular cone. The facets for the neurapophyses are in the form of the figure 8; their internal borders are prominent. The atlas has a broad oval centrum, which is not truncate below, and has no markings of any kind on the under surface. The articular faces for the neurapophyses are prominent, and approach near together. The depression for the occipital condyle is small, circular, and situated above the centre. From Henry's Fork. _Amia depressa_ (?), Marsh. Pr. Ac. Nat. Sc. 1871, p. 103 In this species the dorsal centra are wide, low, and short, and of a regular oval outline. The articular cones are shallow, and have their bottoms but slightly above the centre. The neurapophysial facets are deep, with prominent borders, and the diapophyses are sessile. The chief peculiarity is that the under surface of the centrum has no markings of any kind. _Measurements._ M. Length of centrum ·010 Breadth of centrum ·040 Depth of centrum ·027 As Professor Marsh has given no measurements, the reference to _A. depressa_ cannot be certain. The specimen was found at Henry's Fork. Amia scutata, Cope. Bull, of U. S. Geol. Survey, No. 1 of Series II, p A species of about the size of _A. calva_, but with a proportionately larger head. It is represented in our collection by a specimen which lacks only a portion of the caudal and pectoral fins. The _premaxillary_ is short and stout, articulates closely with the maxillary, and bears a single row of pointed recurved teeth. These are shorter and straighter than in _A. calva_. The _maxillary_ is much as in the modern species, but is rounder. The cranio-facial axis is straight and broad; the _basioccipital_ is the largest of the bones; the _basisphenoid_ and _presphenoid_ are of the usual shape and size, but there is a constriction at their junction which is not marked in the modern species. The _vomer_ is long and double, and at the extremity is armed with rows of small teeth. The two portions diverge more perceptibly than in _A. calva_, and are stouter, though this appearance may, to some extent, be due to flattening.