264 



INEZ L. WHIPPLE. 



FIG. 6. Ventral view of the poste- 

 rior abdominal region of Desitiog- 

 nathus briinleyonim, X 2 - All of the 

 abdominal muscles have been removed 

 except the transversalis muscles and 

 the vestigial ypsiloid muscles of the 

 left side. Abbreviations not previ- 

 ously explained : r>i t median process 

 of pubis ; ya,., vestige of anterior yp 

 siloid muscle ; yp, , vestige of posterior 

 ypsiloid muscle. 



arises from the lateral process of the pubis. From this origin 

 the fibers diverge to their insertion mainly into the linea alba, 

 although in most cases a few are inserted into the first myocomma. 

 When we consider the Cartilago ypsiloidcs of the lunged forms, 

 with its stem in the linea alba and its arms diverging at the first 

 myocomma, it seems very probable that this muscle in the lung- 

 less forms is a vestigial M. 'ypsiloidens posterior which persists 



even after the disappearance of 

 the cartilage to which it was orig- 

 inally attached. In some speci- 

 mens a few fibers of this muscle 

 were found to extend to the sec- 

 ond myocomma and in one speci- 

 men of Dcsmognatlius brimleyorum 

 a separate little muscle (Fig. 6, 

 jw) consisting of a few fibers only 

 was found in the region of the 

 second myotome arising in the 

 linea alba and converging ob- 

 liquely outward and posteriorly. 

 These variable evidences of differ- 

 entiation from the second myo- 

 tome suggest, of course, the 

 probable vestiges of the M. ypsi- 

 loidens (Ulterior. 



Still further evidence of the for- 

 mer existence of an ypsiloid car- 

 tilage in lungless forms is fur- 

 nished by the fact that in its absence the anterior portion of the 

 M. pubo-ischio-femoralis interims originates from the linea alba in 

 the exact region corresponding to the origin from the posterior 

 part of the stem of the ypsiloid cartilage in lunged forms. 



5. Cryptobranchus allegJieniensis. In Cryptobranclms the ypsi- 

 loid cartilage is very well developed and its articulation with the 

 pubis displays marked mobility. It differs somewhat in form 

 from that of the salamanders, in that its lateral arms are very 

 much longer and rapidly broaden toward the outer ends so that 

 they are spatulate in shape (Fig. 7). The cartilage begins to 



