126 NATURAL SCIENCE. Feb.. 



accepted definition of that suborder. The last of the Patagonian 

 Cetaceans is represented by two skulls, which indicate a rather large 

 member of the Delphinidse, with a somewhat elongated snout. This 

 form, which I have proposed to designate by the name oiArgyrodelphis, 

 differs, however, from all existing dolphins in that the hinder teeth are 

 furnished with minute fore-and-aft cusps, thus showing another 

 ancestral feature among the Patagonian Cetaceans. 



Concerning the collection of remains of giant birds from the 

 Santa Cruz deposits in the La Plata Museum, so much has of late 

 years been written, and the plates accompanying the memoir of 

 of Senores Moreno and Mercerat are so excellent, that it will be 

 unnecessary to say much in this place. It is, however, certain that the 

 number of generic names which have been published is much too 

 large, and that the name Phorosrhachus, originally proposed by Sehor 

 Ameghino, has the right of priority. Apart from their gigantic 

 size, these birds claim especial attention on account of the extra- 

 ordinary size and massiveness of their skulls, as attested by the form 

 of the mandibular symphysis, of which there are several examples in 

 the Museum. Although, in the memoir referred to above, these birds 

 were arranged under several family and generic heads, I am in 

 accord with Seiior Ameghino in regarding the whole of them as 

 pertaining to a single family, the larger members of which may 

 be subdivided into two genera, Phorovhacus and Brontornis. In the 

 former the symphysis of the lower jaw was long and narrow, its length 

 when entire being probably about 7^ inches, and its maximum width 

 2^ inches. In the more massively built Brontornis, on the other hand, 

 the sympyhsis was very broad and short, while the margin of the jaw 

 was remarkable for its extreme curvature, the tip being sharply 

 inclined upwards. The approximate length of the whole symphysis 

 is 5-I inches, and the width about four inches. This type of jaw 

 seems quite unlike that of any living group of birds. 



Of the cranium, the Museum possesses two fragments, neither of 

 which are figured in the memoir of Senores Moreno and Mercerat. 

 One of these comprises the occipital and parietal regions, imperfect 

 on the left side, where it shows a cast of a portion of the brain ; while 

 the other is a part of the left side of the cranial box, with the quadrate 

 in position. From the latter I was fortunately enabled to detach the 

 greater part of the quadrate, and was thus able to learn that this bone 

 was articulated to the cranium by two distinct heads, and that it was 

 apparently not overlapped by a descending process of the squamosal. 

 Both these being essentially Carinate characters, it seems evident that 

 the Stereornithes cannot be included in the Ratitae ; and that they 

 must consequently either be placed among the Carinatae or form 

 a group by themselves. 



This group, in which Gastornis may have to be included, will 

 perhaps turn out to form the connecting link between Carinates and 

 Ratites. 



