AVES : REPTILIA. 381 



(1) Odontotormae (Marsh). Vertebrae biconcave ; rami of lower jaw not 



anchylosed ; tail short ; some of the vertebrae fused. Ichthyornis 

 from American Cretaceous strata. 



(2) Post-cretaceous Carinatae. Adult edentulous, but the fossil Argillornis 



longipennis has dental alveoli ; rami of lower jaw anchylosed ; vertebral 

 centra typical ; tail short ; a ploughshare bone. Tertiary, Diluvial 

 and living. 



For the literature of Fossil Birds, see p. 66, ante. 



Teeth in Parrots, Fraisse, Verhandl. Phys. Med. Gesellsch. Wurzburg, xv. 

 1881, SB. p. iii. 



Classification, Newton, ' Ornithology,' Encyclopaedia Britannica (ed. ix.) xviii. 

 1885; cf. Huxley, P. Z. S. 1867-1868; Sclater, The Ibis, 1880; and collected 

 papers of Garrod and Forbes. 



CLASS REPTILIA. 



Cold-blooded Sauropsida with epidermal scales, sometimes combined with 

 underlying dermal bones and then forming scutes ; and not developed as are 

 hairs and feathers in saccular involutions of the integument. The charac- 

 ters of the skeleton vary much but the vertebral centra never possess the 

 typical Avian shape. The sacral vertebrae are usually two, provided with 

 large ribs expanded dis tally. The inter clavicle, when present, never fuses with 

 the sternum which is usually rhomboidal, cartilaginous and more or less ossi- 

 fied but not, as in birds, replaced by membrane bone (? Pterodactyles]. The 

 ilia vary much in the degree to which they extend forwards, and in existing 

 Reptilia usually extend backwards more than in the opposite direction : the 

 ischiaform a ventral symphy sis as do the pub es except in certain of the extinct 

 Deinosauria. The pelvic bones and metatarsalia remain separate except in 

 the extinct Ceratosaurus in which they anchylose. There are always two 

 aortae (right and left], and the ventricle is either single, or double as in 

 Crocodilia where however the venous and arterial blood currents communi- 

 cate at the base of the aortae : there are only two semilunar valves at the bases 

 of the aortae and pulmonary artery. 



The outer layer of epidermic cells is cornified and its cells often contain 

 air. It is thrown off and renewed periodically in Lacertilia and Ophidia. 

 The integument appears to have been smooth in the extinct Plesiosauria and 

 Ichthyosauria, and in the Amphisbaenoidea among Lizards it is divided 

 into rectangular areae disposed in transverse rows. Scales are formed as 

 duplicatures of the integument. The corium (derm) is composed of hori- 

 zontal and vertical bundles of fibres as in the lower Vertebrata. Pigment 

 is not usually found in the epidermis but in special pigment cells of the 

 corium and in many Lacertilia (e.g. Anolis, Chamaeleon] there is a change 

 of colour apparently connected with psychical changes. Dermal bony 

 plates occur in many Lacertilia (e.g. many Scincoidea], often of microscopic 

 size as in the Geckoes (Ascalabotd]. In the Crocodilia these dermal plates 



