Uronautes cetiformis

The cervical vertebra of this species is of unusual form, being short and transverse, and not wider than deep. In Polycotylus latıpinnis this vertebra is much wider than deep, and as long as wide. The neuropophyses are compressed so as to be anteroposterior. and they inclose a rather wide neural canal. The parapophyses are directed equally downwards and outwards, occupying the position of the angle of a subquadrate outline, since the sides are nearly vertical. The articular faces are slightly concave, and the centrum is perforated vertically by the usual two foramina. A dorsal vertebra found in immediate proximity to the cervical just described is much like that of the Polycotylus latipinnis. That is, it is exceedingly short antero-posteriorly, and has concave articular faces, the concavity with flat fundus, and marked with a few obscure concentric grooves. The sides are also slightly concave, and are pierced with a. foramen at the superior portion. The vertical foramina are also present. The neural arch is in this specimen separated from the centrnm, not having become coössified. This circumstance might lead to a doubt as to the proper reference of the specimen to this animal, but such doubt has little foundation. In one of the caudal vertebrae one of the diapophyses is coössified, and the other is not. The suture of the surface thus exposed is of a very fine texture, and evidently not like that seen in the genera where it is to act as a permanent articulation. In the case of the dorsal vertebra, the suture for the neuropophysis has the same character. This vertebra is much larger than the cervical, but does not much exceed the proximal caudal in size; preserving the relations seen in the Polycotylus latipinnis. Adjoining the border of the fossa of the neuropopliysis is a small parapophysial tuberosity. A proximal caudal vertebra has a very small fore and aft diameter, and the vertical exceeds the transverse diameter. The diapophyses spring from the middle of the sides of the Centrum, while the inferior face is separated from the inferior lateral faces by an obtuse longitudinal angle. In general, the form is that of a transverse hexagon. The chevron facets are very slightly developed. Another probably distal caudal vertebra considerably resembles that in the corresponding part of the skeleton of a cetacean. It is without neural arch, transverse, flat below, and with the two lateral faces of unequal length, the superior being the longer. The vertical perforating foramina join at the neural canal, and there is a short subquadrate plane on each side of the latter. There are no indications of chevron facets. These vertebrae are diflerent from any of those yet known in Polycotylus. Measurements. M. antero-postorior Diameter of a. cervical Centrum {vertical transverse. 016. 026. 029 antero-posterior Diameter of a dorsal {vertical transverse. 030. 055. 056 antero-posterior Diameter of a proximal caudal {vertical transverse. 022.040. 062 antero-posterior Diameter of a distal caudal š vertical transverse. 015. 017. 038 Diameter of neural canal of the proximal caudal above mem- sured. 012 Do. of diapoplıysis of do. at base. 018 The distal end of a proximal limb bone is much like the correspending part of Polycotylus latipinnis. It is relatively of large size, flat, and strongly convex at the extremity, which is not transversely’ truncate. A portion of another liinb bone, perhaps belonging to the distal segment, is symmetrical. The shaft is broken off, and displays a large medullary cavity, with thin walls, which soon terminates towards the articular end, in a fundos with a fissure in the bottom. The proximal portion of a rib hus a truncate head of an oval outline. The inferior border presents a low tnberosity, which may represent the capitulum. Measurements. M. Width of distal end of proximal limb bone. 109 Thiekness of the same. 032 longer Diameter of proximal end of a rib {shorter. 030. 028 The bones above described were found together by the writer, on a slope of the cream-colored soft sandstone, which lies above the black shales of Cretaceous No. 4, near Amell's Creek, Montana. I suppose the formation to be the No. 5, or Fox Hills group of Meek and Hayden. Near them were found shark's teeth of the genera Otodus and Lamna. and a species of Enchodus. Above them l found lying loose a fragment of a Baculites.