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.
| 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.
The frontal is long, broad, and thick; the upper surface is delicately sculptured in a somewhat different pattern from that seen in the modern species. The parietal is short and broad, while the epiotic is unusually narrow. The mandible is long and slender; the rami are incurved anteriorly, but apparently not to the same extent as in A. calva. The articular has the shape of a long and narrow wedge; it does not form a very close articulation with the dentary. The dentary is long and comparatively slender, has a rounded outline, and is occupied by an external row of large, and an internal band of small teeth. The mandibular teeth, like those of the upper jaw, are somewhat different from the teeth of A. calva; they are shorter, stouter, and are not so much incurved or recurved. They are very sharp, and show a constriction below the apex. The small teeth are of the usual size and shape. The jugular plate is well developed, and is long and narrow. The hyoid arch is very much the same as that shown in the recent species; the characteristic flat branchiostegals are well marked; they appear to be thirteen in number.
The scapular arch is long and stout. The clavicle is strongly bent, the supra-clavicle is short, and the post-clavicle is long. The pectoral fin is too indistinct for description.
The vertebræ are of considerable depth in the anterior dorsal region, and decrease steadily in size as they go backwards. The neural spines are long and slender, and project strongly backwards. The relation of the centra to the arches seems to be about that seen in A. calva, but the neurapophyses are more slender. The diapophyses are long and slender, in this respect differing from the Bridger species and approaching the modern one. The dorsals are thirty-five in number. The caudals number about forty-seven. They have smaller centra, but longer and stronger neurapophyses than the dorsals. The hæmal arch is long, and the hæmapophyses articulate movably with the centra. The spines supporting the caudal fin rays are very stout. The dorsal fin is long and soft, and has long interneurals supporting short rays; these are fifty-three in number. The anal fin, on the other hand, is very short, having but nine rays, which are long and jointed, and articulate with short interhæmals. The caudal fin appears to be of the usual form. The femur is of the general shape characteristic of Amia, but is not just like that of A. calva. It is shorter, broader at the proximal end, while the distal end is narrower, and has a deeper constriction just above it. The ventral fins are placed under the middle of the dorsal region, and have each ten rays. The scales are of the usual cycloidal shape, and minutely striate.