No. 3.] PELVIS OF THE TESTUDINATA. 359 



— the acetabular bone of the Mammalia.^ This element, I think, 

 originated during the evolution of Mammalia, and may appear 

 in any group. 



Mehnert^ has expressed the opinion that a three-rayed pelvis 

 is the original form for all Amniota. This seems to be correct, 

 with the exception, perhaps, of the oldest Amniota, which seem 

 to have had a continuous gastral cartilage, as in Necturus for 

 instance, in which pubis and ischium became ossified. The his- 

 tory of the vertebrate pelvis seems to be this : — 



1. Continuous gastral cartilage, extending between the femora. 

 Dipnoa, Selachia part. 



2. Continuous gastral cartilage, in which the ischium devel- 

 oped as a separate ossification. Proteida. 



3. Continuous gastral cartilage, in which pubis and ischium 

 appeared as separate ossifications. Batrachia part, Progano- 

 sauria part. 



4. a. Pubic and ischiadic ossifications, extending over whole 

 gastral cartilage, Theromora, permian Batrachia part. Croco- 

 dilia, Pterosauria (i*). b. Gastral cartilage between pubis and 

 ischium disappearing ; appearance of foramina pubo-ischiadica ; 

 all other Amniota. 



1 In the sketch of the pelvis of Dermatemys sent me by Professor Rutmeyer a 

 small acetabular bone is present. 



2 Mehnert, E. : Unterstichungen Uber die Entwicklung des Beckengiisteh bei 

 eiiiigen Sailgethieren. Morph. Jahrb., XV, p. ill, also Morph., Jahrb. XIII. Meh- 

 nert's latest publication treats about the development of the pelvis in Eniys orbicu- 

 laris, L. (Morph. Jahrb., Vol. XVI, Part 4). The account of the phylogeny of the 

 pelvis of the Testudinata given in this paper will modify some of the opinions 

 expressed by Dr. Mehnert. 



Clark University, Worcester, Mass. 

 February 6, 1S91. 



