1890.] : Zoology. 483 
iensis Grandid., the type of my Erymnochelys, generically the same 
as Podocnemis. 
The genus Dumerilia was established by Grandidier, but since 
this name had been used different times before, I introduced the name 
Erymn ochelys (Zool. Anz., No. 285, 1888.) After this, Boulenger 
claimed that Erymnochelys mihi (Dumerilia, Grandid.) was a synonym 
of Podocnemis. In No. 296 of the Zool. Anz., 1888, I gave the 
generic characters which distinguish Erymnochelys from Podocnemis. 
I said in Erymnochelys the jugal is in extensive connection with the 
quadrate ; this connection is absent in Podocnemis ; in Erymnochelys 
the prefrontals are produced in front and without median groove ; the 
cervical vertebrz form single condyles. In Podocnemis saddle-shaped 
vertebrz, as in birds, are present. 
In the general shape of the skull Peltocephalus resembles Macro- 
chelys ; Peltocephalus is in the same relation to Erymnochelys, as 
Macrochelys to Chelydra. Morphologically the skulls of Erymnochelys 
and Peltocephalus are very much alike; but Peltocephalus has the 
saddle-shaped cervicals of Podocnemis, 
The atlas of Podocnemis is entirely different from that of Pelto- 
cephalus and Erymnochelys. In Podocnemis the first intercentrum is 
small and free. In Erymnochelys and Peltocephalus it is large and 
internally united with the neuroids and the centrum of the atlas. 
I give now a table of the characters of the three genera: 
i Podocnemis, Wagler. 
Jugal and quadrate bones separated ; articular faces of anterior cer- 
vicals saddle-shaped ; first intercentrum small and free. Type: 
expansa, Schweigg. 
Peltocephalus, Dum. and Bib. 
Jugal and quadrate in contact ; articular faces of anterior cervical 
saddle-shaped ; first intercentrum large and suturally united with neur- 
oids and centrum of atlas. Interparietal shield triangular with base 
behind. Type: P. tracaxa, Spix. 
Erymnochelys, Baur. 
Jugal and quadrate in contact ; articular faces of cervicals not sad- 
dle-shaped ; first intercentrum large and suturally united with neuroids 
and centrum of atlas. Interparietal shield triangular with base in 
front. Tpye: Æ. madagascariensis, Grand 
Note.—The condition of the atlas in Peltocephalus and Erymno- 
chelys, must be considered as one from which the condition seen in the 
