CASTOROIDID^— CASTOROIDES— C. OHIOENSIS. 425 



extinct Horse and the Mastodon. There is also in the Museum of Compara- 

 tive Zoology 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, and 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 the 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.- r >0) ; distance between orbits, 2 83 ; 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 7 00, 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 Stimpsou to Professor Agassiz some 

 years siiee, 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. 



