I20 



NATURAL SCIENCE. Feb. 



ways, and has tardily abolished some of the superfluous genera 

 made by himself and his colleagues. His repentance comes, however, 

 too late— after all the mischief has been done ; and even then it is 

 but half-hearted. He maintains, for instance, the genus Acvothevinm, 

 which is merely founded on specimens belonging to some of the 

 three species of Nesodon, with a superfluous premolar tooth, probably 

 caused by the first premolar having come up in front of the corre- 

 sponding milk-molar, instead of replacing it ; while the Ust of nominal 

 species remains as long as ever. South American palaeontological work 

 has, indeed, already become a bye-word in England, but it is really 

 far worse than I had any idea of previous to my visit to La Plata ; 

 and it may be worth the coasideration of the Council of the Zoological 

 Record whether it will not for the future be advisable to omit all 

 mention of the majority or the whole of the names proposed by the 

 Argentine palaeontologists to whom I refer, as being mere useless 

 encumbrances, instead of aids, to science. 



Passing from this unpleasant portion of my subject to more 

 agreeable matters, I may now call attention to two very remarkable 

 members of the Toxodo^nt Suborder, both being animals not larger 

 than a rabbit, and exhibiting most marked rodent resemblances. The 

 one of these is Hegetothevium from the Santa Cruz beds of Patagonia, 

 and the other Pachyrucus from the deposits of Monte Hermoso. The 

 latter of the two is distinguished from its ally by the tympanic bullae 

 being situated on the superior aspect of the skull and is so Rodent- 

 like in general form and structure that it is almost difficult to beUeve 

 that it is not an ally of the hares. It is, however, as shown by its 

 teeth, clearly a member of the Toxodont Ungulata, and since it is 

 perfectly evident that such an animal cannot have been the ancestor 

 of the Rodentia, it follows that the Rodent resemblances presented by 

 the more speciaHsed Toxodonts must be due to parallelism. 



By many writers the Toxodonts have been placed, with the Pro- 

 boscidea and certain extinct suborders, in the Subungulata ; they 

 have, however, the alternating carpus of the Perissodactyla and 

 Artiodactyla, coupled with the linear tarsus of the Proboscidea, 

 while the astragalus is but slightly grooved, and the calcaneum carries 

 a large facet for the fibula, as in the suborder last mentioned. These 

 features clearly indicate that the Toxodonts (which are further 

 characterised by some or all of their teeth growing for the greater 

 portion or the whole of Ufe) must form a subordinal group of equal 

 rank with the Artiodactyla, Perissodactyla, and Proboscidea. 

 Another subordinal group of extinct South American Ungulates, 

 for which I have suggested the name Astrapotheria, is formed by the 

 genera Homalodontotherium and Astrapotherium. Differing from the 

 Toxodonts in having their teeth rooted at an early age, these Ungu- 

 lates are further distinguished by having a perfectly flat astragalus 

 with a head at the lower end for the navicular, while it is probable 

 that both the carpus and tarsus were of the Unear lype. The cheek- 



