CASTOROIDID Z—CASTOROIDES—C. OHIOENSIS. 425 
extinct Horse and the Mastodon. There is also in the Museum of Compara- 
tive Zodlogy an excellent cast of a very large skull, from an unknown locality, 
but probably from either Illinois or Michigan.* Its known habitat hence 
extended from Texas to Michigan, and thence eastward to Western New 
York and South Carolina. Its remains appear to have been found only in 
the Quaternary deposits, aud in several instances have been found associated 
with those of the Mastodon, and also with those of the extinct Horse and 
Megatherium, with which animals it was doubtless a contemporary. 
Of the Clyde specimen (of which I have before me a cast), Dr. Wyman 
has published the following measurements: Length, 10.50 inches; greatest 
width, 7.20; transverse diameter of the occiput, 5.50; vertical diameter of 
the occiput, 2.60; distance between the orbits, 1.90; distance between the 
_ anterior (first) molars, 0.30; between the last molars, 1.80. The length of 
the molar series in tne cast is 2.50; length of the nasal bones, 3.63; greatest 
width of the nasals, 2.07. The cast of a much larger and evidently older 
specimen, but unfortunately imperfect, lacking the incisors and the zygomatic 
arches, gives the following measurements: Length, 11.75 (with the incisors 
restored, 12.50); distance between orbits, 283; transverse diameter of the 
occiput, 6.70; vertical diameter of the same, 3.25; nasals, length, 4.12; 
greatest width, 2.55; upper molars, length of the series, 2.87. Though so 
much larger (one-fifth) than the Clyde specimen, the difference is readily 
accounted for by the difference in age. 
According to Foster, the lower jaw found at Nashport measured 9 inches 
2 lines (9.16) from the front border to the condylar process, and 3 inches 8 
lines (3.67) from the base to the coronoid process. The Clyde example, 
according to Wyman, had a length of 700, and a vertical depth, measured 
from the top of the coronoid process, of 3.75. The Memphis specimen, 
according to Wyman, was still larger; the length of the molar series 
being 3.10, against 2.75 in the Clyde specimen and 2.80 in the Nashport 
specimen. Foster gives the length of the lower incisor in the Nashport 
specimen, measured along its outer curve, as 11.50. One of the fragments of 
a lower incisor from Dallas, Texas, has a transverse diameter of nearly an 
inch (0.95), while the antero- posterior diameter | is still greater (1.05). 
* This cast was taken from a skull loaned by Messrs. Foster and Stimpson to Professor Agassiz & some 
years since, and returned recently to the Chicago Academy of Sciences. No record accompanies the cast, 
and all the above-named gentlemen being now dead, it is difficult to learn the history of the original 
specimen. 
