DESCRIPTION OF GROUPS AND SPECIES. 43 
DESCRIPTION OF GROUPS AND SPECIES. 
Order TESTUDINES Batsch. Turtles and Tortoises. 
Reptiles with the body relatively short and broad. Quadrate bone immovably joined to the 
pterygoid, the prootic, and paroccipital; its outer surface excavated to form a tympanic cavity. 
Paroccipitals not consolidated with the exoccipital. Vomer single, if not missing. Pterygoids 
closing the palate by their inner borders. Teeth never present; the jaws always armed with a 
horny covering. Nasal opening single. Dorsal ribs each with a single head; at least the anterio1 
ones intervertebrally attacht. A nuchal bone always present. Cervical vertebra eight; dorsals 
ten. Epiplastra (clavicles) and at least six other bones present in the abdominal wall. No 
sternum or sternal ribs ever developt. Each half of the pelvis composed of three bones, all con- 
tributing to the acetabulum. Four limbs always present. Humerus with ectepicondylar passage. 
This order of Reptilia is divided into two suborders, the ATHEC# and the 
‘THECOPHORA. 
Suborder ATHEC Cope. 
Turtles which retain the primitive dermal armor, with at least traces of the subdermal 
expansions connected with the ribs. 
Of this suborder there is no known representative from North American 
deposits, unless possibly certain dermal bones that have been found to accompany 
the remains of Basilosaurus (Zeuglodon) belonged to some otherwise unknown 
species of the group. This is improbable, however, as shown by Dames (Pal. 
Abhandl., v, 1894, p. 220). In Europe the suborder is represented by Eosphargis, 
of the London Clay of England, by Psephophorus, of the Oligocene and Miocene ot 
the Continent, and perhaps by Pseudosphargts, of the Upper Oligocene of Germany. 
The latter genus is based on a very imperfect skull; and, while presenting many 
resemblances to Dermochelys, is not regarded by the present writer as being at all 
certainly a member of the Athece. This turtle possest descending plates from the 
parietals to the pterygoids. 
Suborder THECOPHORA Dollo. 
Turtles in which the primitive dermal armor has become obsolete or abolisht. Always a 
more or less complete carapace formed by at least the expansions of the ribs, the nuchal bone 
and with rare exceptions a series of neurals; usually a very complete shell formed by the bones 
mentioned, together with series of peripherals and a varying number of plastral bones. Skull 
always furnisht with descending parietal plates. 
This suborder, containing the vast majority of turtles, living and extinct, 
consists of four superfamilies, the AMPHICHELYDIA, the PLEURODIRA, the CryPTo- 
pirA, and the TRIoNYCHOIDEA. Of the first there are no living representatives. 
Kry To SUPERFAMILIES OF | HECOPHORA. 
1. Mesoplastra present or absent. If absent, hinder lobe of plastron with rough scars for umion with 
pelvic bones except in Plesiochelyide. 
a'. Mesoplastra always, so far as known, present; no plastrall/scais.r-..2 ae Amphi helydia 
a’. Mesolpastra present or absent; rough scars on hinder lobe of plastron Pleurodira 
2. Mesoplastra always absent; no sutural scars on plastron. 
a’. Peripheral bones always present....-..-+--+---+2+25+000- TEBE Cryptodira 
a’. Peripheral bones present only in one genus now existing. ae Trionychotdea 
Superfamily AMPHICHELYDIA Lydekker. 
Thecophorous turtles having a carapace composed of neural, costal, and peripheral bones 
and a plastron in which the epiplastra are in contact with the hyoplastra. Mesoplastra usually, 
perhaps always, present. Intergular and inframarginal scutes probably always developt. 
