CLASSIFICATION. a5 
THE CLASSIFICATION OF THE TURTLES. 
It is not the purpose of the writer to give here an account of the various schemes 
of classification that have been proposed by writers on the turtles. For such an 
account the reader may consult the third part of the sixth, volume of Bronn’s 
Klassen und Ordnungen des Thierreichs, beginning with page 347. The following 
is the arrangement of suborders, superfamilies, and families accepted by the writer. 
All of these families, except those in italics, have fossil representatives. 
Orver Testudines. 
SuporpDeER I. Athecz. 
Famity. Dermochelyide. 
SusorpeR II. Thecophora. 
SurERFAMILY 1. Amphichelydia. 
Famutigs. Pleurosternida, Baénide, Plesiochelyida ? 
SUPERFAMILY 2. Pleurodira. 
Famities. Bothremyide, Pelomeduside, Chelyide, Miolanide. 
SUPERFAMILY 3. Cryptodira. 
Famities. ‘Thalassemydide, ‘Voxochelyide, Desmatochelyide, Protostegida, Cheloniide, 
Tretosternida, Chelydrida, Dermatemydide, Platysternide, Kinosternide 
Carettochelyd, Emydide, ‘Testudinide. 
SupeRFAMILY 4. Trionychoidea. 
Famiuies. Plastomenide, Trionychide. 
The arrangement and names of the suborders and superfamilies above given 
are the same as those used by Mr. George A. Boulenger in his Catalogue of the 
Chelonia of the British Museum, 1889. Mr. Richard Lydekker employs practically 
the same groups in his Catalogue of the Fossil Reptilia of the British Museum, 
part 11, 1889; but to some of his groups are given different names. Dr. Louis 
Dollo, of Brussels, also divides the turtles into the two suborders Athece and 
Thecophora. Altho this eminent writer believes that Dermochelys, the only living 
representative of the Atheca, was derived from the Cheloniidz, he separates it as 
the representative of a distinct suborder on account of its extreme modifications of 
structure. It was Cope who first proposed to make this turtle the type of a distinct 
suborder. 
In his Bibliography and Catalogue of the Fossil Vertebrata of North America, 
1902, the present writer assigned to the ‘Trionychoidea, under the name Trionychia, 
the rank of a suborder. A further consideration of the subject has convinct him 
that these turtles should rank lower than a suborder; not higher than a super- 
family. Indeed, they appear to have brancht off from the earliest Cryptodira; 
but their lineage is so ancient, and they have undergone so many modifications of 
structure, that they are of equal rank with the Cryptodira. The skull is more like 
that of the Cryptodires than that of the Pleurodires, but has developt peculiarities 
of its own. Like the Cryptodires, the temporal roof has never been eaten away from 
below, and always a zygomatic arch remains. The neck is wholly cryptodiran in 
its modifications and is retracted within the shell in the same way. This isa feature 
unique among animals, and it seems improbable that it could be hit upon independ- 
ently by two distinct groups of turtles. The pelvis in its parts and its relationships 
to the shell is entirely cryptodiran. 
Ernst Haeckel, in his Systematische Phylogenie der Wirbelthiere, 1895, page 320, 
has taken the position that the Trionychoidea had probably arisen already in the 
Triassic and that they are to be lookt upon as the group from which all the The- 
cophora have been derived. That the group was establisht even in the Trias is 
possible; that it gave origin to the other groups of Thecophora seems quite impos- 
