Vol. 56.] ARISIODBSMUS RUTIMEYEKI. 645 



establish the reptilian characters of the skull of Orniihorhynchus by 

 examining the skull of a young male in the Physiological Series of 

 the Koyal College of Surgeons, No. 323 c 1 in November 1895. I 

 desire also to reiterate my thanks to the Trustees of the Basel 

 University Museum. 



Discussion. 



Mr. C. W. Andrews inquired whether he rightly understood 

 the Author to state that he considered that affinity exists between 

 the pterodactyl Ornithocheirus, the mammal Echidna, and the pro- 

 posed new Anomodont genus. He also asked the precise difference 

 between the term ' Theropsida ' proposed by the Author, and the 

 terms ' Sauromainmalia ' of Baur and ' Hypotheria ' of Huxley. 



Mr. E. T. Newton also spoke. 



The Aothor, in reply, said that the late Prof. Cope had given 

 evidence of the close relationship of the Labyrinthodontia with the 

 fossil Eeptilia in the fact that some Permian fossils originally 

 referred to the former group had subsequently been recognized as 

 Anomodonts ; and it had been shown that in some Labyrinthodont 

 genera like Eryops, there was little if any difference to separate the 

 shoulder-girdle from the Anomodont type. He was unable to recog- 

 nize any differences of more than ordinal value between Ichthyo- 

 sauria and typical Labyrinthodontia in the structure of the palate 

 of the skull, both having a long median parasphenoid with similarly 

 formed pterygoid bones, denning the palatal vacuities. He thought 

 that the presence of supratemporal bones behind the orbits in 

 Labyrinthodonts and Ichthyosaurs is as striking a coincidence of 

 structure in the lateral condition of the skull. The vertebra of 

 Eosaurus and other genera, and the ribs, show that in vertebral 

 characters the resemblances between some Labyrinthodonts and 

 Ichthyosaurus are as close as are the resemblances between any 

 orders of existing reptiles. He believed that the structure of 

 Theriodonts and other Anomodonts now made the reptilian nature 

 of Labyrinthodonts more intelligible. 



He preferred the term * Theropsida ' to ' Sauromammalia ' or 

 ' Hypotheria,' because those were hypothetical terms not based 

 upon structures known when they were suggested. The discovery 

 of the reptilian character of the malar arch, and of the presence of 

 prefrontal and postfrontal bones in the skull of Orniihorhynchus in 

 1895, had given a new importance to the resemblances between the 

 bones of oviparous Monotremata and the Anomodont reptilia, and 

 these facts were expressed for the first time in the name ' Theropsida.' 



With regard to the diagram shown on the screen, in which the 

 femur of the proposed new Anomodont was placed between the corre- 

 sponding bones of Echidna and Ornithocheirus, the diagram was meant 

 to suggest a relationship between Ornithosaurs and Monotremes, 

 both of which have prepubic bones. He first indicated resem- 

 blances between Anomodonts and some Ornithosaurs in a memoir 

 upon Prolorosaurus. 



1 Sir Kichard Owen figured a still younger skull in fig. 172, p. 371, article 

 Monotremata, in ' Todd's Cyclopaedia of Anatomy & Physiology ' vol. iii. In 

 tli at skull the postfrontal is named alisphenoid. 



