New Fossil Beptiles. 37 



Diapsidans and retained in the Pareisaurians, but lost in the 

 Anomodonts. The condition in the TherocephaUans is unknown. 

 The condition of the rib head does not help us much. In Pareia- 

 saurus the cervical ribs are double-headed, the dorsal single-headed. 

 In Anomodonts differentiation of the heads is carried further back, 

 but the lower dorsal ribs are still single-headed ; and in most other 

 early reptiles the ribs are also single-headed. 



The presence of abdominal ribs is a most important and unlooked- 

 for character. Hitherto no one has detected abdominal ribs in any 

 Anomodont, Cynodont, Therocephalian or Pareiasaurian, and in the 

 Anomodonts at least we may be pretty certain they were not deve- 

 loped. They are present in Plesiosaurs, which some hold to be 

 related to the TherocephaUans and to belong to the Synapsidan 

 phylum. But if we place the Plesiosaurs, as I believe ought to be 

 done, in the Diapsidan phylum, then it may be affirmed that ab- 

 dominal ribs are only known among the Diapsidans, and they are 

 probably invariably present in the more primitive groups. They 

 are present in the Pelycosauria, the Mesosauria, the Procolophonia, 

 and the Proterosauria, to mention only the oldest groups, and they 

 are retained in many of the younger. The occurrence of them in 

 Galechirus seems to suggest an early Diapsidan affinity of the 

 primitive Synapsidans. 



The pelvis in structure is much more Diapsidan than Synapsidan. 

 The pubis and ischium are of the ordinary plate-like type found in 

 all the early Diaptosaurians. In Pareiasaurus we have a pelvis 

 which is clearly a modification of the same type, but it is greatly 

 specialised, and in the Anomodonts and Cynodonts the modifications 

 are so great that it is difficult to recognise any evidences of the 

 plate-like type. Unfortunately little is known of the pelvis of 

 the TherocephaUans. Prof. Amilitzky has sent me a photograph 

 of the skeleton of the Eussian Therocephalian Inostransewia, y^hich 

 seems to have a small ilium not unlike Galechirus, but it has not 

 yet been figured or described. Of the Dinocephalians only the ilium 

 of Titanosuchus is known. In Pareiasaurus, the Anomodonts and 

 Cynodonts the ilium is greatly expanded and directed forwards. In 

 Galechirus it is not much expanded and directed backwards. In 

 Titanosuchus the iliac crest is also short, and not much directed 

 forwards. On the whole the pelvic characters of Galechirus are 

 almost typically Diapsidan. 



From the above discussion of the various characters it will be 

 seen that in Galechirus we have a Synapsidan reptile showing 

 affinities with both the TherocephaUans and the Anomodonts, but 

 much more primitive than either, and a form which retains a 



