250 Royal Society : — 



to such an amount of change as might take place in the progress of 

 growth of a tooth with a constantly renewable pulp. Professor Owen 

 finds at least no good grounds for inferring a specific distinction be- 

 tween the mature if not old Scelidothere from Buenos Ayres, and the 

 younger specimen from Patagonia. 



The author then proceeds to give a detailed anatomical account of 

 the fossil bones in the British Museum, instituting a comparison 

 between them and the bones of other large extinct animals, especially 

 those of the Edentate order. 



The Scelidothere was a quadruped of from 8 to 1 feet in length, 

 but not more than 4 feet high, and nearly as broad at the haunches ; 

 the thigh-bones being extraordinarily broad in proportion to their 

 length. The trunk gradually tapered forwards to the long and 

 slender head. The fore-limbs had complete clavicles, and the rota- 

 tory movements of the fore-arm. All the limbs were provided with 

 long and strong claws. The animal had a long and muscular tongue, 

 and it is probable that its food might have been of a more mixed 

 nature than that of the Megatherium. But it was more essentially 

 related to the Sloths than to the Ant-eaters. 



In conclusion the author remarks, that as our knowledge of the 

 great Megatherioid animals increases, the definition of their distinctive 

 characters demands a more extended comparison of particulars. Hence 

 in each successive attempt at a restoration of these truly remarkable 

 extinct South American quadrupeds, there results a description of 

 details which might seem prolix and uncalled for, but which are 

 necessary for the proper development of the task of reproducing a 

 specimen of an extinct species. 



Professor Owen adds, that he is indebted to an allotment from the 

 Government Grant, placed at the disposal of the Royal Society for 

 scientific purposes, for the means of laying before the Society large 

 and admirably executed drawings of the fossil bones described in his 

 paper. 



January 29, 1857. — Major-General Sabine, Treas. and V. P., in the 



Chair. 



" On the Nervous System of Lumbricus terrestris." By J. Lock- 

 hart Clarke, Esq., F.R.S. 



In the summer of 1855, with the view of throwing some light on 

 other researches in human anatomy, in which he was already en- 

 gaged, the author undertook some anatomical inquiries on the nervous 

 system of Invertebrata ; but finding them occupy more time than he 

 could spare, he was compelled to relinquish the pursuit after having 

 made many interesting but desultory observations on various animals. 

 As he had proceeded, however, to a considerable extent with the 

 nervous system of Lumbricus ferrestris, and discovered in it much 

 that is important and was hitherto unknown, he has thought it expe- 

 dient to resume and complete this portion of the subject without 

 further delay. 



