66 DESCRIPTIONS OF PREPARATIONS. 



and Histology, i. p. 363. For a figure of Iguanodon, see Moseley, Nature, xxviii. 

 1883, p. 441; or Dollo, op. cit. supra, PI. v. Cf. Hulke, Journal Geol. Soc. xl. 1884, 

 p. 53; and Huxley, Anatomy of Vertebrated Animals, 1871, pp. 223-228. 



The process of the ischium which divides the obturator foramen into two 

 portions is very large in the Deinosaur Laosaurus. The upper division of the 

 foramen transmits in birds the tendon of the obturator internus muscle, a rather 

 curious point. 



Of the segments of the hind-limb, the femur is remarkably short and very 

 broad in Hesperornis and the Divers ; while the tibio-tarsus is of great length in 

 Ratitae and Waders. The fibula is as long as the tibia in Archaeopteryx. It is 

 so at one time in developing birds but shortens subsequently. The tarsal element 

 of the tibio-tarsus has been found by Baur to appear in the embryo chick as two 

 bones, a tibiale and a fibulare, corresponding to the tibia and fibula respectively. 

 The tibiale develops an ascending anterior spur, while the tibia broadens out so 

 as to cover the fibulare, and the fibula itself shortens. The two tarsal bones 

 subsequently unite. According to Morse the ascending process corresponds in 

 the embryoes of certain birds representing various groups (Alcidae, Laridae, &c.) 

 to a separate intermedium. If this is so, there are three proximal tarsalia in some 

 birds, each with its own ossific centre. The ascending spur of the tibiale 

 (? = astragalus) is present in Deinosauria. The bony arch confining the extensor 

 tendons in the Pigeon as they pass over the tarsal region of the tibio-tarsus is 

 ligamentous in Ratitae. This ligament is united at one end to the tibia, at the 

 other to a bony projection apparently developed on the fibulare (=calcaneum) 

 both in the Ratite and the young Carinate. It probably corresponds to the 

 anterior annular ligament of the human foot. The distal tarsal elements are 

 represented by a single cartilage which corresponds eventually to the second, third, 

 and fourth metatarsalia. The rudimentary fifth metatarsal fuses with it (Baur). 



The metatarsalia in Archaeopteryx are apparently free, or but slightly anchy- 

 losed. In Penguins the three metatarsalia (ii., iii., iv.) are short and lie parallel 

 to one another. They are not raised from the ground in them nor in Auks and 

 Divers. Mt. iii. is the largest as a rule, but Mt. iv. is as large in some birds and 

 much larger in Hesperornis. The calcar of the Fowl ossifies independently, 

 but fuses with Mt. iii. Mt. i. is only anchylosed to Mt. ii. in Phaethon. All the 

 toes are united by a common web in the embryo a condition which persists in 

 the Pelican, Cormorant, Solan Goose, and Divers. They rarely all retain their 

 primitive forward position, e. g. in the Penguin, Swift, &c. The hallux is sometimes 

 absent. 



Aves, Selenka and Gadow, Bronn's Klass. und Ordn. des Thierreichs, vi. 

 Abth. iv. Birds, W. K. Parker and A. Newton, Encyclopaedia Britannica, 

 (ed. ix.) iii. Oiseaux fossiles de la France, &c., Milne-Edwards, 2 vols. and Atlas, 

 Paris, 1867-71. Eappareil locomoteur des oiseaux, Alix, Paris, 1874. Palatal 

 and other characters. Huxley, P. Z. S. 1867, 1868. 



Pigeon. T. J. Parker, Zootomy, London, 1884, p. 182. 



Fossil Birds. Archaeopteryx. Dames, Palaeont. Abhandl., Berlin, ii. part 3, 

 1884. Marsh, Nature xxv. 1881-82. Vogt, The Ibis, 1880. Owen, Ph. Tr. 

 153, 1863. Cf. Baur, Z. A. ix. 1886, for complete lit. Odontornithes (Hesperornis, 

 .Ichthyornis). Marsh, Memoir, United States Geological Exploration, 4oth parallel, 



