1889.] Geology and Pal(Eontology . 715 
The Horned Dinosauria of the Laramie. — Since my last note 
on this subject (American Naturalist, December, 1888, page 11 08), the 
publication, by Professor Marsh, of a figure ^ of a skull of one of the 
species, enables me to determine more exactly the affinities of sev- 
eral species of the family which have been in my possession for many 
The most complete skeleton in my collection is that of the Alono- 
clonius crassus Cope.^ This includes representatives of all the elements 
excepting the bones of the feet. The posterior part of the skull is pre- 
served, including the left frontal bone. This bears a horn over the 
middle of the orbit, of small dimensions, and with the apex antero- 
posteriorly compressed. The parietal bones are enormously expanded, 
and are interrupted on each side of the middle line by a huge foramen, 
which causes the remaining parts of the bone to resemble the corres- 
ponding parts of Chamaeleo, depressed in a horizontal plane. The 
squamosals are lateral, and consist of a wide plate with convex external 
border with a slightly undulating outline. The ilium is remarkably 
elongate, both anterior and posterior to the acetabulum, appropriate to 
the ten vertebra which constitute the sacrum. It and the sacrum 
resemble very closely those of the Agathaumas sylvesfre Cope,^ which 
fact, with the evidence derived from the other vertebrae, leaves no 
doubt that the Agathaumas is to be referred to the family of horned 
herbivorous Dinosauria, with Monoclonius and Polyonax. This family 
is called by Marsh the Ceratopsidae ; but as it is not certain that Cera- 
tops, Marsh, is distinct from one of the genera previously named, I 
shall call it the Agathaumidse (or hellenice Agathaumantidse), from the 
longest known genus, Agathaumas. 
The characters of Polyonax Cope are not yet fully known. The 
frontal horns of the typical species, F. mortuarius^ Cope, are long and 
slender, while those of the known species of Monoclonius are shorter 
and robust, and there is a large nasal horn. The Agathaumas sylvestre 
is the largest of the species. 
I now give a list of the species of this family known to me ; 
2 Proceedings of Academy, Philadelphia, October, 1876. AMERICAN NATURALIST, 
1886, page 154. 
of the West. 1875. page 54. plates v. vi. 
* Bulletins U. S. Geological Survey Terrs., 1874, April ; Cretaceous Vertebrata of the 
