448 ANATOMY OF VERTEBRATES. 



and then come those of the ureters. 1 The urogenital compart- 

 ment opens into the vestibule by a narrow fissure, the lower part 

 of which is continued into the groove of the penis or clitoris 



lyino; in the vestibule. 



/ ~ 



The cloacal outlet, commonly termed the ( anus,' varies in shape 

 in Rcptilia, but is more constant in position than in Pisces ; it is 

 never so far forward as in some of that class. In tailed Batrachia 

 it is a longitudinal slit in the axis of the trunk ; in anourous 



o ' 



larvae it is protected by folds of membrane, which unite to form 

 the lower border of the tail-fin ; during the progress of absorption 

 of this natatory organ the anus is somewhat advanced, and assumes 

 a rounded form with a sphincter. In the Sea-snake (Pelamys} 

 the anus is longitudinally bilabiate, but the anterior part of the 

 fissure is crossed by a semilunar fold or ridge. In Lizards the 

 corresponding fold, with its scaly covering, is larger, covers more 

 of the orifice, and gives it a transverse semilunar shape. It has a 

 similar form in the Turtle. In Emys it is a puckered aperture, 

 with a tunical border beneath the base of the tail ; in Trionyx it 

 is a longitudinal orifice, and nearer the end of the short tail. In 

 the Iguana the posterior valve of the cloacal opening is approxi- 

 mated, and applied to the anterior one by a muscle which arises 

 from each angle of the fissure or fold between the tail and the 

 thighs. The dilatation of the orifice is produced by two pairs of 

 muscles, attached, the one to the femoro-caudal fold, the other to 

 the lower surface of the tail. 



76. The Liver of Reptiles. This organ is proportionally 

 large in all Reptiles : its form is mainly governed by that of the 

 body. In Serpents, fig. 300, 0, it is unilobate, long, and slender ; 

 in Tortoises, fig. 302, i, it is short and broad, chiefly composed of 

 two subequal lobes; in Lizards, fig. 292, k, it offers an inter- 

 mediate form. 



In the Lepidosiren the liver consists of one long lobe, with a 

 transverse notch on the left side, lodging the gall-bladder. In 

 the Siren the liver presents a similar form, with the addition of a 

 small left lobe at the anterior end. In the Amphiume the long 

 and slender subtrihedral liver extends through nearly two thirds 

 of the abdominal cavity, and the gall-bladder is an inch distant 

 from the lower end. In the Menopome the liver is shorter and 

 broader, with the gall-bladder lodged in a fissure which makes 

 the posterior end bifurcate. In the Newt the liver has a similar 

 terminal notch into which a peritoneal fold enters. In the Frog 



1 xx. vol. i. no. 747, vol. iv. no. 2438. 



