THE YPS1LOID APPARATUS OF URODELES. 



2 59 



view of the posterior abdominal ]region, with the skin and exter- 

 nal oblique muscle removed from the left side. In the mid 

 line, extending anteriorly from the pubic symphysis through 

 the width of a single myotome 

 is the stem portion of the Carti- 

 lago ypsiloidcs (r), the two lat- 

 eral arms of which are hidden by 

 the rectus abdominis. The first 

 myotome of the rectus abdomi- 

 nis, counting anteriorly from the 

 pelvic girdle, is differentiated 

 superficially into two portions, 

 the more Ventral and lateral of 

 which (ra} extends outward with 

 its fibers converging to their in- 

 sertion into a process at the 



OUter edge of the pubis, which I FIG. I. Ventral view of Diemyc- 



Shall call the lateral process of h' llts virutescens, posterior abdominal 

 ,, , TU- 4.- 11 region, V T.. The external oblique 



the pubis. This portion is well 



muscle has been removed from the left 



differentiated into a distinct mus- 

 cle, and in its insertion is closely 

 associated with the posterior por- 

 tion of the external oblique. The 

 second portion (rb} is partially 

 covered by the first, and its fibers 

 slant medially to their insertion 

 into the ventral surface of the 



stem of the ypsiloid cartilage and the anterior margin of the 

 pubis. When the more ventral of these two muscles is removed, 

 it is found that the medial portion of the deeper muscle takes its 

 origin from the lateral arm of the ypsiloid cartilage, which ex- 

 tends obliquely nearly across the second myotome. In Fig. 2 

 both of these muscles have been removed, as well as that portion 

 of the second myotome which lies over but unattached to the 

 Cartilago ypsiloides. On the right side in the figure may be 

 seen two muscles connected with the cartilage. One of these, 

 which may be designated the M. ypsiloidcns posterior (yp\ is a 

 strongly developed muscle which arises from the anterior margin 



side. Abbreviations : ex, M. obliquus 

 externus ; _/, M. pubo-ischio-femoralis 

 externus ; yf, M. pubo-ischio-femoralis 

 internus ; in, M. obliquus interims; 

 /, lateral process of pubis ; /, pubis ; 

 ra, and rb, differentiations of the first 

 myotome of the rectus abdominis ; y, 

 ypsiloid cartilage ; ya, M. ypsiloideus 

 anterior. 



