STEREORNITHES 905 



remains, mostly of gigantic size, found in the Tertiary strata of Santa 

 Cruz in Patagonia. They were considered to combine the characters 

 of Anseres, Herodiones and Accipitres, to shew a transition from the 

 Anatidm to the VuUuridse, and to be separable into nine genera, which 

 were grouped in four Families. In a critical review of this memoir, 

 published in the same year, Dr. Florentino Ameghino (Eevist. Argent. 

 Hist. Nat. i. pp. 441-453) came to the conclusion that the whole 

 series of remains might be referred to two genera, Phorarhacos ^ and 

 Brontornis, both included in the family Phororhacidse, which he placed 

 among the Ratitx, a third genus, named Opisthodadylus from a 

 peculiarity in the position of the facet for the hallux, being at the 

 same time proposed. These views were provisionally accepted by 

 the present writer {Ihis, 1893, pp. 40-47); but an examination of 

 the specimens in the Museum of La Plata induced him {Nat Sc. 

 1894, p. 125) to consider the retention of the Order Stereornithes 

 desirable, and also to declare that the Santa Cruz beds were in all 

 probability not older than the Upper Oligocene ; while here it may 

 be mentioned that the group of Birds is also represented in the 

 somewhat newer deposits of Monte Hermoso near Bahia Blanca. 

 The most important information regarding these Birds is that given 

 in 1895 by Dr. Ameghino [Bolet. del Inst. Geograf. Argent, xv. 11, 

 12), where a considerable number of their remains, obtained by his 

 brother in Patagonia, are figured ; the validity of the group Stereor- 

 nithes is admitted, and nine genera^ are referred to it, Fhororhacos 

 with six species, Pelecyornis with three, Brontornis with one or two, 

 and the others with one each ; all but Opisthodadylus, which is 

 regarded as forming a distinct Family, being grouped as Phororhacidse. 

 The most conspicuous peculiarity of the Stereornithes is the 

 enormous size and ponderous structure of the skull, which is quite 

 unlike that of any recent Bird, and seems out of all proportion to 

 the limbs, gigantic as are some of the leg-bones. The upper jaw is 

 remarkable for its extreme lateral compression, and yet is of great 

 depth, its extremity terminating in a hook, while that of the man- ^ > J 



dible turns upward.^^ There is no ossified interorbital septum, and ^f' ' "^ '^f^ 

 the orbits apparently communicate with the preorbital vacuity, ' ' 



while the nostrils, which are situated high up, are pervious. The 



^ This, with the spelling Phorysrhacos, had been originally described in 1887 

 by Dr. Ameghino {Bolet. Mus. de la Plata, i. p. 24) from its mandible as an 

 Edentate Mammal ; but its ornithic nature was declared by him four years later 

 {Eevist. Argent. Hist. Nat. i. p. 255). As to the etymology of the name, con- 

 jecture only can be entertained. Tliat which is next to it in point of time is 

 31'esembriornis, Moreno {Progresos del Mus. la Plata, p. 29. Buenos Aires : 1889.) 



2 These are by no means the same as the nine before proposed by Senores 

 Moreno and Mercerat, all but two of which are submerged, while others are 

 proposed. 



^ Senores Moreno and Mercerat figured the mandibles as upper jaws (0^. cit. 

 pis. V. fig. 3, vi. fig. 2, viii. fig. 4, ix. fig. 2, pp. 20, 21). 



