

1891.] Recent Literature. 645 
under-mentioned genus '’ (Trachyaspis). The fact is, that, as I showed 
in 1873 (Ann. Report U. S. Geol. Surv. Terr., 1872, p. 621), Adocus 
has an intergular plate, and a simple contact of the inferior pelvic 
bones with the plastron, and is allied to Baéna, belonging therefore to 
Lydekker’s group Amphichelydia ; and the absence of rib-heads is not 
included in my family definitions. Also Agomphus has no trace of 
vermiculation, while they are strong in Trachyaspis. 
We refer to some points of nomenclature which arrest our attention, 
The author establishes a ‘“ new family,” Dermatemydidz, and then 
remarks that the ‘‘so-called Adocidz’’ belong to it. Should this be 
the case, the proper proceeding would have been to have placed Derma- 
temys and allies in the Adocide. The name Anomodontia is used 
instead of Theromora for the order first defined by the present critic 
under the latter name. Both Prof. Owen’s first and last use of the 
former term are shown by Lydekker to have been for the division to 
which the later name Dicynodontia has been also applied. The latter 
name should be disused, both because it is a synonym and because 
some of its members are edentulous. Dr. Lydekker is probably correct 
in preferring the name~Theriodonta to that of Pelycosauria, as they 
may refer to the same natural division, although the evidence is not 
all in yet. The name Cotylosauria, though proposed with an erroneous 
definition, is probably the proper one to apply to the subdivision 
Pareiosauria, while Proganosauria should be probably used in place o 
Procolophonia. The term Labyrinthodontia is resuscitated and used 
for the Stegocephali, although its original definition and etymology 
render it applicable to a limited subdivision only, whose actual bounda- 
ries are not yet known. In the division of the Stegocephali into orders 
or suborders considerable difference of opinion has developed. The 
obvious and simple division into Ganocephali, Rhachitomi, Embol- 
omeri, and Microsauri is objected to by Lydekker, Zittel, and Fritsch, 
on grounds which seem to the present critic insufficient ; and the classi- 
fications which it is proposed to substitute appear to stand on unsecure 
foundations. The value of the presence of complete intercentra in the 
cervical and dorsal regions in Embolomeri is said to be destroyed by 
the fact that Archegosaurus (Ganocephali) possesses the character in 
the caudal region; very inconsequent reasoning, it appears to us. 
Objection to the systematic importance of the segmented or rhachi- 
tomous structure is based on the fact that it is present in young Laby- 
rinthodons, etc. “This is certainly a new reason for discarding a char- 
acter from systematic biology. When a character is shown to be 
inconstant in adults it should be relegated to the rear, but not before. : 





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