144 ifs Jabs JOBIOS 
chiefly of small, rounded eminences, with some ridges. The inner 
surface is rather smooth. 
With regard to the nomenclature of the mandible it may be stated 
that the one generally accepted is here used. As is well known 
Baur (Anat. Anz., Vol. XI, 1896) attempted to modify the classifi- 
cation of the bones by applying the name of angular to a long splint- 
like element in front of the articular instead of to the bone previously 
designated by this name. This necessitated a shifting of names and 
Baur called the angular “‘splenial” and the splenial ‘‘presplenial.”’ 
Baur’s primary mistake lay in his accepting the turtle as the basis 
of nomenclature while the original nomenclature was based on the 
crocodile. 
Kingsley has since (Am. Nat., 1905, pp. 59 ff.) corroborated 
Baur’s observations as to the origin of these bones and, taking the 
crocodile as the standard, has retained the names of the bones as 
originally given by Cuvier and Owen. ‘Thus he designates the 
so-called splenial of the turtle of authors, the splenial of Baur, the 
“‘dermarticular.” 
Williston had, however, previously discussed this bone from the 
plesiosaurs (‘‘North Am. Ples.,” Field Col. Mus., Geol. Ser., Vol. ° 
II, No. 1, 1903, pp. 29-32) and had given it the name of prearticular. 
This name should then have priority over that of Kingsley. The 
prearticular is apparently absent from the crocodiles, while it is a 
distinct bone in plesiosaurs, dinosaurs, turtles, and some other early 
reptiles. 
THE ILIUM 
This bone presents features which distinguish it quite markedly 
from that of Rhytidodon as figured by McGregor. The acetabulum is 
quite broad and must have been quite largely contained by the ilium. 
Above the acetabulum is a strong process which rises fully two inches 
above the depth of the cavity. It is of triangular cross-section and is 
formed by the junction of three ridges, two of which bound the aceta- 
bulum and form its upper walls, while the third extends obliquely 
forward toward the upper anterior corner of the bone. This ridge is 
very strong where it rises up to aid in forming the process, but it thins 
distally and does not quite reach the anterior extremity. The upper 
anterior process has a rounded outline and, unlike Rhytidodon, its 
