626 SLODILES: LOK: SIODLIENASS, 
primitive of the land-living reptiles, we may find a reason for the 
widespread distribution of the group. 
The Cynodontia.— Under this head is grouped the majority 
of the South African forms, all except those that by their skull 
structure approach very nearly to the Mammalia. The forms 
considered here are the ones placed in the families Galesauride 
and the Zapinocephalide by Lydekker, in the catalogue of the 
fossil reptiles of the British Museum, under the suborder of 
Theriodonta. The group at first glimpse seems very like the Pely- 
cosauria, but there is one very important distinction. The two 
postorbital arches of the first group have disappeared and are 
replaced by a single one that is either made up of the union of 
the two primitive ones, or is the single one left after one of them 
has disappeared; in all probability the first of these cases is the 
toue one, Whe teeth areiof carnivorous type, recurved andaim 
many cases differentiated into incisors, canines, and molars. 
These forms are exclusively from the Karroo formation of 
South Africa. The position of this formation is not definitely 
known. alt is) either Permianvom Bermo-riassic, livtheyevic 
dence of the vertebrate remains is to be taken, it should be 
placed as far up in the geological time scale as possible, for 
there are-found in these beds remains that are very closely 
related to forms that are found in the Lower Cretaceous of the 
United States. 
Galesaurus, known from the skull only, was a small, lizardlike 
animal; the skull was depressed, with a rather long muzzle and 
very large temporal vacuities. The teeth were differentiated into 
the incisors, canines, and cheek teeth. The cheek teeth were 
furnished with small lateral cusps at the base. The whole skull 
was nearly four inches long. 
Aleurosaurus is also known only from the skull. The muzzle 
is long but quite high, resembling in this respect the nasal por- 
tion of Dimetrodon. The teeth are simple and without the lat- 
eral cusps. There is a single large tusk in the upper jaw in the 
position of a canine. The posterior part of the skull is abruptly 
truncated, as in the previous suborder. 
