1893.] Zoology. 673 
quadrate and basisphenoid; epipterygoid free or not free; dentary 
bones united. Cervical vertebra with rudimentary transverse processes 
in front of vertebra ; the posterior cervicals with double articular faces ; 
sacral ribs well-developed and connected with centrum and neuroids. 
Pelvis free from plastron and carapace. Epiplastra in contact with 
hyoplastra ; entoplastron oval, rhomboidal or T-shaped, a more or less 
complete series of peripheralia more or less connected with the ribs. 
I.—CHELONIOIDEA. 
A parieto-squamosal arch; no foramen palatinum between palate 
and maxillary ; articular faces between the sixth and seventh cervical 
plane ;-nuchal with a distinct process on the lower side for the articu- 
lation with the neuroid of the eighth cervical; no lateral processes of 
nuchal. One biconvex cervical vertebra. 
1. Cheloniide. 
Skull with. descending processes of parietals; limbs paddle-shaped ; 
claws one or two. Chelonia, Thalassochelys, Caretta, Lepidochelys. 
2. Dermochelyide. 
Skull without descending processes of parietals; limbs paddle- 
shaped; no claws. Bony carapace dissolved into numerous mosaic-like 
pieces. Dermochelys. 
II. —CHELYDROIDEA. 
No parieto-squamosal arch; a foramen palatinum between palate 
and maxillary ; articular faces between the sixth and seventh cervicals 
not plane; nuchal without lower process, but with more or less strong 
lateral process underlying the peripherals; one biconvex cervical; a 
. complete series of inframarginals.’ 
1. Dermatemydide. 
Frontals not excluded from orbit; maxillary without connection 
with quadratojugal; squamosal without connection with postfronto- 
orbital ; mesogastroid well-developed, separating completely entopubes 
and entoischia; number of peripherals 11; an entoplastron. Number 
of neuralia incomplete; the posterior pleurals not meeting in median 
line. Dermatemys. — - ; 
2. Chelydride. 
Frontals exeluded from orbit; maxillary without connection with 
quadratojugal ; squamosal in connection with postfronto-orbital; meso- 
1 Some species of Kinosternon excepted. 
