82 DESCRIPTIONS OF PREPARATIONS. 



There is a remnant of the notochord in the middle of the centrum of each 

 vertebra. A small tubercle, very rudimentary in the Frog, projects in some Am- 

 phibia, most of all in Urodela, from the centrum of the first vertebra, and fits into 

 a pit in the basi-occipital condyle. It has been supposed in consequence that the 

 first vertebra represents an axis, and that an atlas is fused with the skull, or rather 

 has disappeared, leaving a slight trace behind. The urostyle in Bombinator igneus 

 appears from Gotte's researches, to be derived from (i) three vertebrae, the x th , 

 xi th , xii th , and (2) a rod of cartilage which lies below the notochord. In the animal 

 when of adult size, the x th vertebra has a pair of nerve foramina behind it ; the 

 xi tb has a similar pair, not found in the Frog, and the xii th has the neural canal 

 opening behind its arch. The notochord behind the vertebrae atrophies. 



The part of the shoulder-girdle termed clavicle by Gotte, consists of a cartilage 

 bar with a membrane bone overlying it. Bar and membrane bone constitute the 

 praecoracoid of W. K. Parker. The bone is the clavicle, the cartilage the prae- 

 coracoid of Gegenbaur. The bar is at first, as in the Chelonia, according to Gotte, 

 a process of the scapula which grows ventrally, fuses medianly with the coracoid, 

 and gives rise to a little mass of tissue which fuses with its fellow and forms the 

 episternum as well as the connecting cartilage which unites the two halves of the 

 shoulder-girdle ventrally. This connecting cartilage represents the posterior pro- 

 longation of the Lacertilian interclavicle. The hyposternum, according to Gotte, 

 is not formed, like the sternum of higher Vertebrata, from the ventral ends of ribs, 

 but by a chondrification of the membrane uniting the epicoracoids (median cartilage 

 borders of the coracoids). In Bombinator and Urodela other structures are added, 

 viz. in the former a pair, in the latter sometimes more, e. g. in Menopoma three 

 pairs, of cartilage bands lying in the linea alba and intersections of the recti abdo- 

 minis muscles. Gotte compares them to the false ribs of the Crocodile and 

 Hatteria, but Ruge (M. J. vi. 1880, p. 369) suggests that they are rudiments of 

 the ventral ends of true ribs. 



The ileum, according to Hoffmann, is an ileo-pubis. In a young Dactylethra 

 capensis he found the symphysial portion to contain a pubic ossification fused in the 

 adult to the ileum. In the middle line there was a projecting rod-like epipubis, a 

 structure generally present in Urodela. In the Frog a pubic ossification appears to 

 be absent, but Hoffmann mentions in Rana and Bufo ' a flat, thin, fairly strong 

 tendon,' with the same attachment as the epipubis. The obturator nerve which 

 perforates the cartilage in Urodela and marks off the pubis, passes over, i. e. outside 

 the pubic region in the Anura, 



It is not certain whether or no the cuneiform in the carpus represents the 

 ulnare and intermedium as it does in some Urodela. The carpalia 3, 4, 5, do not 

 always fuse in Anura. The astragalus and calcaneum are in some genera separate. 

 The sixth toe is very commonly present. In a young R. temporaria it consists of 

 a tarsale, and of a metatarsal with two phalanges which ultimately fuse, but remain 

 separate in R. esculenta. The sixth and first toe bear nails in Rhinophrynus 

 dorsalis, as they do with the addition of the second and third toes in Xenopus 

 laevis. 



Skeleton in general, see Hoffmann, Huxley, Ecker and Wiedersheim, p. 78, 

 ante. 



Skull of Anura. W. K. Parker, Ph. Tr. 166, 1876; 172, 1881. 



