100 HAY-—VERTEBRATES OF CARBONIFEROUS AGE, [March 16, 
ured as having a pair of conspicuous pads or bosses on the posterior 
part of the upper surface of the base. C. girtyi shows nothing what- 
ever of this character. The only structure of this kind is the pair 
of protuberances found on the front of the lower surface of the 
base. The lateral cusps of C. mortifer aré also said to possess 
sharp cutting edges and strong, sharp strie. Good figures of 
C. mortifer may be found in St. John’s paper in Hayden’s Final 
Report of the Geology of Nebraska, Pl. iii, Fig. 6, and Pl. vi, 
Fig. 13; and inthe posthumous paper by Dr. Newberry, Z7ans. 
WV. Y. Academy of Sciences, vol. xvi, Pl. xxii, Figs. 2-2*. 
Cladodus occidentalis Leidy also is marked by a pair of bosses 
on the hinder part of the upper surface of the base. The distinct- 
ness of C. mortifer from C. occidentalis is questionable. 
SAGENODUS. 
In making a study of the scales of this genus I have had, thanks 
to the generosity of the authorities in charge of the vertebrate 
collections of the United States National Museum, access to the 
type specimens of the species described by Prof. E. D. Cope in a 
posthumous paper published in volume xxxvi of the PROCEEDINGS 
OF THE AMERICAN PHILOSOPHICAL SOCIETY, in the year 1897. 
Besides these scales, there are a few others belonging to the 
National Museum, which were presented, as were Prof. Cope’s 
types, by Mr. Lacoe; but which Prof. Cope seems not to have 
examined. I have also had the privilege of examining still other 
specimens of the genus, which had been obtained from Mazon 
creek, Illinois, by Mr. L. E. Daniels, and which yet belong to his 
private collection. All these have been carefully studied and 
compared. The result is that I recognize as valid seven out of the 
ten species described by Prof. Cope. This writer relied much on 
the forms of the scales in his identifications of the species ; but a 
close examination of a series of scales will quickly shake one’s 
confidence in the validity of this character. I have examined also 
the scales on a specimen of the existing Ceratodus, with which 
Sagenodus was certainly closely allied, and I find that there is a 
considerable variation in the forms of the scales on different parts 
of the body. In the region near the shoulder-girdle they are 
usually broad and with truncated posterior border; toward the 
tail the scales are more elongated and pointed. Besides these, the 
head is covered with a few very large scales which differ in form 
