i894. THE LA PLATA MUSEUM. 127 



Their vertebrae were highly pneumatic ; but the hollow leg-bones 

 appear to have been devoid of pneumatic foramina, and during life 

 were probably filled with marrow, like those of existing Ratitae, In 

 Brontornis the tibia has a length of 30 inches, while the metatarsus 

 measures i5f inches in length, with a width of 5-|- inches at the upper 

 end, and 3 inches in the middle of the shaft. Although displaying a 

 similar depression at the upper part of the front of the shaft, the 

 metatarsus of Phororhacus is a much more slender bone, the length in 

 one species being 15^ inches, with a maximum width at the upper 

 end of 3J inches, and of i-| inches at the middle of the shaft. 



The much smaller imperfect metatarsus figured under the name 

 of Palaociconia is regarded by Sefior Ameghino as inseparable from 

 Phororhacus ; but from the circumstance that the foramen between 

 the third and fourth trochleae perforates the bone at right angles, 

 instead of descending obliquely so as to open inferiorly on the lower 

 aspect of the bone between the two trochleae, I am inclined to think 

 that it has a right to generic distinction. 



The whole of the remains noticed above are from formations of 

 Tertiary age, but the collection of fossil vertebrates does not end 

 with that period. From certain deposits in the districts of Chubut 

 and Neuquen, in Patagonia, which are probably of Cretaceous age, 

 there have been obtained a large series of Dinosaurian bones 

 pertaining to reptiles rivalling in size their most gigantic European 

 and North American allies. One of these creatures, although by no 

 means the largest, I have referred, in a memoir about to be published 

 by the Museum, to the genus Titanosaimis, originally founded, on the 

 evidence of caudal vertebrae, from the Cretaceous rocks of India. 

 These vertebrae differed from those of all other gigantic Dinosaurs in 

 having a cup at the anterior end of the centrum, and a ball at the 

 opposite extremity, thus resembling those of existing crocodiles. 

 The large series of specimens in the La Plata Museum serves to 

 show that Titanosannis, as had been previously suspected, is really 

 a member of that group of Dinosaurs to which the name of Sauropoda 

 has been applied. This is clearly shown by a fine dorsal vertebra 

 exhibiting the v/ell-known lateral pits characterising that suborder. 



In these vertebrae, it may be observed, the cup is situated at the 

 hinder end of the centrum, and the change of type is effected by 

 means of the first caudal vertebra, which, as in crocodiles, is 

 biconvex. The bones of an enormous fore-limb, together with an 

 imperfect lemur and two caudal vertebrae, indicate a still more 

 stupendous member of the same family, for which I have suggested 

 the name of Argyrosaiirus. In the type specimen the length of the 

 humerus is nearly the same as in the gigantic humerus 

 from the Kimmeridge Clay preserved in the British Museum, and 

 mentioned in the Catalogue of Fossil Reptiles under the name of 

 Pelorosanrns hunierocristatiis. A smaller Dinosaur, characterised by the 

 slight development of the lateral pits in the vertebrae of the trunk. 



