450 Zoological Society. 



facts just mentioned. The cause of these curious changes in the 

 shape of the blood- discs is well- deserving of further inquiry. 



The blood- corpuscles of the Aurochs are scarcely distinguishable 

 in any respect from those of its congener the Bison and of some other 

 large ruminants. 



Of the Edentata, as far as can be inferred from the few yet exa- 

 mined, the mean size of the blood- corpuscles is larger than in mam- 

 mals generally. And in the genus Bradypus, as fully explained in 

 the Proceedings of the Zoological Society, June 11, 1844, I found 

 those corpuscles larger than any yet observed in Mammalia, with the 

 single exception of those of the Elephant. This large size of the 

 blood-corpuscles of the Sloth is confirmed by the measurement now 

 given of them, from a younger animal than that which afforded me 

 the blood for the former observations. 



Judging from the facts at present ascertained, the marsupial ani- 

 mals appear to agree in the size and form of the blood-corpuscles 

 with the corresponding placental Mammalia, as mentioned in my 

 notice in the Dublin Medical Press, November 1839, and in the Pro- 

 ceedings of the Zoological Society, June 8, 1841 . But in the Mar- 

 supials further observations are required. The measurement now 

 given of the blood-corpuscles of the Crab- eating Opossum accords 

 with the view just stated. 



The following measurements of the blood-corpuscles of Birds tend 

 to confirm the result which I have before published, that in this entire 

 class the law for the size of the corpuscles is the same as in a single 

 family of Mammalia ; and that the short diameter of the oval blood- 

 corpuscles of Birds has a general correspondence with the diameter 

 of the circular blood- corpuscles of mammals. 



Through the kindness of Dr. Andrew Smith, I am enabled to add 

 measurements of the blood-corpuscles of such reptiles as were alive 

 some time since in his very interesting and valuable collection. 

 Laland's Megalotis (Otocyon Lalandii, [Desm.]) .... 1-3600 



Meminna Deer (Moschus Meminna, Erxl.) 1-12325 



Red Brocket Deer (Cervus nemorivagus, Cuv.) 1-7060 



A Brocket Deer (Cervus — a new species) 1-7125 



Aurochs (Bos Urus, Bodd.) 1-4074 



A young Sloth (Bradypus didactylus, Linn.) 1-2778 



Anteater (Echidna kistrix, Cuv.) 1-3300 



Crab-eating Opossum (Didelphis cancrivora, Temm.). . 1-3436 



Red-legged Falcon (Falco rufipes, Bechst.). . . . <j ^Vy* ■, 070Q 



Long-eared Owl (Otus vulgaris, Flem.) < c Y) i 3400 



Little Owl (Strix passerina y Temm.) I S D 1 3555 



Red-backed Shrike (Lanius collurio, Linn.) .. < g'^* , 387s 



Cassowary (Casuarius emu, Lath.) < S D 1 2800 



Great Bustard (Otis tarda, Linn.) I S D 1 3200 



