Ceratops paucidens.
The specimen recently described by the writer under the name Hadrosaurus pauciaens[1] should probably be referred to the genus Ceratops, as a comparison with more perfect specimens indicates a much closer affinity with that genus than at first supposed. In addition to the maxillary described, one of the premaxillaries is in good preservation. This agrees in general features with the corresponding bone in Triceratops, but is less specialized. Its inner surface is deeply concave, showing that the two premaxillaries did not meet each other closely, as in Triceratops, but apparently only in front. This species, as well as the type of the genus, Ceratops montanus, represents smaller, less specialized forms of the family, and may be from a lower geological horizon than the gigantic reptiles which the writer has recently made known.
In addition to. the special characters of the Ceratopsidæ shown in the skull, as stated by the writer in this Journal (vol. xxxviii, p. 505), the following features seen in other parts of the skeleton may be mentioned:
(1) The atlas and axis, and one or more adjoining cervical vertebral are coössified with each other.
(2) Their cervical ribs are likewise firmly united with the same vertebral.
(3) The remaining cervical vertebræ are short, and have the articular faces of the centra nearly flat.
(4) The trunk vertebræ have very short centra, with flat articular ends. Above the centra, they resemble the vertebræ of Stegosaurus.
(5) The sacrum was strengthened by union with several adjacent vertebral.
{6) The caudal vertebral are short and rugose, and the tailwas of moderate length.
(7) The ilium is elongated, especially in front; the ischium slender, and directed backward.
(8) The pubis extended forward, and its posterior branch was wanting.
(9) The limbs were short and massive, and all four were used in locomotion.
(10) The feet were all provided with broad hoofs, as in Stegosaurus.
(11) The bones of the skeleton all appear to have been solid.
(12) Dermal ossifications were present, and some species were protected by heavy armor.
- ↑ This Journal, vol. xxxvii, p. 336, April, 1889.
