THE VPSILOID APPARATUS OF URODELES. 



263 



alba. It does not show in the myotome anterior to the pubis 

 the superficial differentiation noted in the forms already described. 

 Neither is any of this superficial portion attached to the ypsiloid 

 cartilage. 



The musculature of the Cartilage ypsiloides is otherwise quite 

 similar to that of Dicniyctylns. The anterior ypsiloid muscle, is, 

 owing to the great width of the linea alba, inserted into the distal 

 portion only of the arms. The relation of the M. pubo-ischio- 

 fcinoralis interims to the ypsiloid 

 cartilage is the same as that already 

 described in the preceding cases. 



4. Desmognathus brimleyonnii, 

 D. fuse a, Spclcrpcs ruder, S. bilinc- 

 atits, Plethodon erythronotus, P. 

 cincrcns. In none of these forms 

 is there a Cartilago ypsiloides. The 

 musculature of the posterior ab- 

 dominal region gives, however, 

 decided evidence of the former ex- 

 istence of an ypsiloid apparatus. 



The abdominal wall shows a 

 more primitive musculature than 

 Diemyctyhts, the metamerism being 

 much more strongly marked. The 

 rectus abdominis is broad and powerful. In the myotome 

 (Fig. 5, r) immediately anterior to the pubis there is the same 

 superficial differentiation that Dieinyctylns and other lunged forms 

 exhibit. There is one difference, however, which is due to the 

 fact that the anterior border of the pelvic girdle is deeply incurved 

 on either side of the ventral midline so that the border presents 

 a conspicuous median and two lateral processes (Fig. 6, / and ;;/). 

 As a result of this the medial portion of the rectus abdominis 

 extends much farther posteriorly than the lateral portion, since 

 it is inserted into the ventral surface of the girdle somewhat 

 posterior to this incurved edge. 



In all of the lungless forms dissected the deeper portion of the 

 first myotome of the rectus abdominis shows a well defined 

 though not at all strongly developed portion (Fig. 6, ,)'/<') which 



FIG. 5. Ventral view of the pos- 

 terior abdominal region of Desmog- 

 n ai hits brimliyoriiiii, X 2 - The M. 

 obliquus externus has been removed 

 from both sides and the M. pubo- 

 ischio-femoralis externus from the 

 right side. 



