42 BAUR. [VOL. I. 



In 127 specimens the ilium was therefore attached either to 

 the i Qth vertebra 83 times, or to the 2Oth 34 times, or to 

 the i gth and the 2Oth obliquely 8 times, or to the 2Oth and 

 2 ist obliquely once. 



The reason of this variation is this : The ilium is attached 

 very loosely to the sacral ribs by ligament, as in Proteus and 

 AmpJiinma. There are no distinctly modified sacral vertebrae, 

 and hence it is not surprising at all that the ilium is not attached 

 always to the same vertebra. The sacral region has not the 

 power of developing sacral ribs at several points on both right 

 and left sides, but the pelvis may attach itself - - for it be- 

 comes secondarily united with the vertebral column - - to 

 any of the vertebrae of the pelvic region. In Nectums we 

 have all the variations possible for the attachment of two 

 consecutive vertebrae, the I9th and 2Oth ; only in one case 

 the ilium reaches the 2ist vertebra, and in this case the pelvis 

 is oblique. 



The Amphibia are descended from fishes in which the pelvis 

 is never in connection with the vertebral column. In Nectums 

 and Proteus the ilium is very loosely connected with the distal 

 processes of the sacral ribs. Necturus and Proteus belong to 

 the Proteida, the only group of living Amphibia with a free 

 paroccipital [opisthotic]. The attachment of the ilium to a 

 definite vertebra has not yet become constant. If one hundred 

 specimens of a lizard, of a crocodile, or of a turtle should be 

 examined, exceedingly few variations would be found. The 

 great variability in the attachment of the pelvis to the vertebral 

 column in the tailed Amphibia is a result of the loose connec- 

 tion between both. Very many more cases of asymmetrical 

 sacra have been described in the tailed Amphibia, than stated 

 by Parker, who knows only that of Lucas ('86, p. 561) in 

 Cryptobranchus (Mcnopoma). They were described as early as 

 1818 in Triturus (Molgc) cristatus Laur. by C. A. S. Schultze 

 ('18, p. 379), and in 1825 by Cuvier ('25, p. 414) ; in Triturus 

 vulgaris L. and Salamandra salamandra L. (inaculosa Laur.) by 

 Clans in 1876 ('76, p. 23) ; in Megalobatrachus maximus Schlegel 

 by Schmidt, Goddart, and Van der Hoven in 1862 ('62), by 

 Claus in 1876 ('76, p. 29) ; in Cryptobranchus (Menopoma) 



