Zoological Society. 281 



any other animal, excepting perhaps the Land Tortoise. The 



Indians have a great dread of coming in contact with this animal, 

 and after disabling him in the chase, never think of approaching him 

 till he is quite dead." (Waterton's Wanderings in South America, 

 171.) 



That muscular irritability exists to a similar extent in the Sloths 

 will be proved by the following extract : — 



"Cormotum suum valdissime retinebat postquam exemptum erat 

 a corpore, per semihorium ; exempto corde, ceterisque visceribns 

 multo post se movebat et pedes lente contrahebat sicut dormituriens 

 solet." (Pison. Hist. Bras. p. 322, quoted by Buffon ; translation by 

 Smellie, 1791, vol. vii. p. 161.) 



7. In the Sloths and Weasel-headed Armadillo the absence of the 

 os tinea?, and the consequent formation of a single tube by the uterus 

 and vagina, approximate these organs very nearly to the oviduct of 

 the Reptilia (see Owen, Zool. Proc. ii. 131, and on the Generation 

 of Marsupial Animals in Phil. Trans. 1834, p. 365). 



In the genera Bradypus, Dasypus, Manis and Myrmecophaga, 

 *' the utero-sexual canal," to use the words of the last-quoted me- 

 moir, " is formed, as in the Tortoises, by a continuation of the urethra 

 or urinary bladder, into which the genital tube opens by a small 

 orifice." 



8. There is yet another highly important character, one indeed 

 which has probably a relation to the preceding, which displays the 

 intimate relationship of the Edentata and Reptiles, namely the ex- 

 treme simplicity of the brain. In the Armadillos, Manises and Ant- 

 eaters, the cerebral hemispheres are devoid of convolutions, whilst 

 in the Sloth they present a few anfractuosities (Owen, Phil. Trans. 

 1834, p. 361). 



9. Professor Owen says, in his elaborate memoir on the Mylodon 

 robustus, that the presence of a persistent formative organ of the teeth 

 of the Megatheroids indicates a property in which they resembled the 

 Reptiles, viz. longevity (p. 166). And again, the intimate structure of 

 the soft dentine of the teeth of the Iguanodon resembles that of the 

 extinct Megatherium and of the recent Sloths (Owen's Odontography, 

 ]). 251). Is it not an idea which forcibly impresses on us the unity 

 of the great plan of nature, that had a comparative anatomist existed 

 in the days of the Megatherium and Iguanodon, he might have dis- 

 covered from an examination of their teeth two common characters, 

 and might thence perhaps have inferred those very relations which 

 in the present paper I have been seeking to enforce with regard to 

 their congeners of another age — almost another world ? 



10. It is well known that the blood-corpuscles of the Reptiles are 

 remarkably large ; the Sloths are the largest yet known amongst the 

 Mammalia, with the single exception of the Elephant. Perhaps 

 however this may be a character of little importance in elucidating 

 the natural affinities of groups, as we find the corpuscles of the Ar- 

 madillo rather smaller than Man's, and those of the Monotremata 

 of about the same size as the human (Gulliver on Blood-corpuscles, 

 Zool. Soc, October 14, 1845). 



Ann. fy Mag. N. Hist. Vol. xviii. X 



