1SS9.J 4-/J . [Cope. 



Remarks. 



1. The average inclination of the first hundred (in 



the order of distance) is 8° 8' 42.CG" 



Of the second hundred 8 58 38.87 



Of the last eighty 7 51 20.15 



And that of the whole two hundred and eighty. 8 21 34.87 



2. The inclinations in the edges of the ring are less than the average. 



3. Other minima are found about the distances 2.44 and 3.09. The 

 maximum between 2.36 and 2.40 is distinctly marked. 



4. As in the case of other planets, the inclinations vary, though with 

 extreme slowness. It has not been shown, however, that the average will 

 change to any great extent. 



5. This average compares thus with certain other inclinations : 



Mercury's orbit 7^ 00' 



Plane of the Sun's equator 7 15 



Average inclination of asteroidal comets 16 40 



6. The maximum inclinations of Mercury and Mars are 10° 36' and 7"^ 

 28' * respectively. The table indicates that the mean inclination of the 

 asteroids has not differed greatly from the mean inclination of Mercury. 



A Review of the North American Species of Hippotherium. 



By E. D. Cope. 

 {Read before the American Philosophical Society, May 3, 1SS9. ) 



The relation of this genus to the other genera of Perissodactyla was in- 

 dicated by Kowalewsky in his work on the genus Anthracotherium, pub- 

 lished in the " Palseontographica " for 1874. He there showed that the 

 genus occupies a place between Anchitherium and Equus in the genealog- 

 ical phylum, as it does in geological time. In a paper on the "Systematic 

 Arrangement of the Perissodactyla, "f the present writer placed Hippo- 

 therium in the family Palaeotheriidte, in a subfamily Hippotheriinge, which 

 was defined as follows: "Bicipital groove of humerus double; molars 

 with cement in the valleys." This subfamily embraces the genera Hip- 

 potherium Eaup, and Protohippus Leidy. The Palseotheriidae is here 

 only distinguished as a whole from the Equidse by the presence of per- 

 fect second and fifth digits. 



The place of Hippotherium in the line of ancestry of the genus Eqnns 



*Stockwell's Mem. on the Sec. Var. of the El. of the Eight Pnnc. Phmct<. Smith. 

 Contrib. to Knowl., •-'32, p. 116. 

 t Proceedings Americau Philos. Soc, 1881, p. 39'J. 



