388 ORNITHOKHTNCIIIDJ!. 



claws, the anterior broad and blunt, the posterior compressed and 

 pointed. Beak smooth, evenly rounded, its junction with the head 

 marked, both above and below, by a projecting leathery flap, 

 evidently developed to save the face from injury when the head is 

 plunged in mud or gravel. Beak, excluding the flap, rather shorter 

 than the rest of the head. 



Skull as already described. 



Horny plates two in number on each side of each jaw ; but the 

 anterior are far less prominent and markedly specialized than the 

 posterior. The former are long and narrow, and each forms a 

 single longitudinal horny ridge, some 13 to 18 miUim. in length, 

 which is placed on the side of the palate about 10 or 15 millim. 

 from its fellow, and with its anterior point about level with the 

 hinder end of the dumbbell-shaped bone. The surface of the bone 

 beneath these plates-is quite smooth, and not modified in any way 

 for their support. The posterior plates are situated just below the 

 level of the orbits, and each consists of a single broad horny and 

 cuspidate plate, subdivided by transverse ridges into a small antero- 

 internal and two large posterior portions. In the lower jaw the 

 plates have the same shapes as in the upper, except that the anterior 

 are longer, and that the posterior have their smallest subdivision 

 behind instead of in front. The bone below the posterior plates, 

 both above and below, is broadened and excavated for the reception 

 of their projecting cuspidate bases. 



Vertebrae: — Cervical 7, dorsal 17, lumbar 2, sacral 2, caudal 

 20 or 21 ; total 48 or 49. 



Habits. Aquatic, fossorial ; feeding on water-insects, Crustacea, 

 moUusca, &c. 



Mange. That of the only species. 



There appears to be no reason to suppose that there is more than 

 a single species of Ornithorhynchus, the marked diiTerence in size 

 between the sexes and a certain variability in colour and texture 

 of fur being apparently responsible for the considerable number of 

 names that the common species bears. 



1. Ornithorliyachus anatiuus. 



Platypus anatiuus, Shaw, Nat, Misc. x. pis. 385 & H86 (animal, 

 beak, &c.) (1799) ; id. Oen. Zool. i. pt. i. p. 229, pis. 66 & 67 

 (animal &o.) (1800) ; Turt. Linn. 8. N. i. p. 30 (1806); Gerrard, 

 Cat. Bones Mamm. B. U. p. 288 (1862) ; Ch-ay, P. Z. 8. 1865, 

 p. -385 ; id. Handl. Edentates, p. 29 (1873). 



Ornithorhynclius paradoxus, Blumenb. Voigfs Mag. Naturk. ii. 

 p. 205 (1800) ; Home, Phil. Trans. 1800, p. 432, pis. xviii. & 

 xix. (beak, skull, &c.) ; id. op. cit. 1802, p. 67, pis. ii.-iv. (anat.) ; 

 Calhoen, Nat. Verh. Bat. Maatsch-Wet. ii. pt. i. p. 177 (1803); 

 I)esm. N. Diet. d'H. N. (1) xxiv., Tahl. MUh. p. 27 (1804); 

 Blumenb. Abbild. Nat. Gegenst. no. 41 (animal) (1810) ; G. Fisch. 

 Zoogn. iii. p. 689 (1814) ; G. Cuv. £. A. i, p. 227 (1817) ; F. Cuv. 

 Dents Mamm. p. 202, pi. Ixxxiii. (horny plates) (1825) ; E. Geoff. 



