DR VAN BEMMELEN ON THE REPTILIAN SKULL. 1 63 



surface, these may be attributed to secondary processes, and no 

 system of bars, like that of RhynchocepJialians and other Reptiles, is 

 derived from them. The quadrate having changed its function " 

 (having become, after Gegenbaur's opinion, the incus), " the zygo- 

 matic bar starts from the squamosum, and in this structure the last 

 remnant of the lateral osseous belt of the head, that sprung up in 

 fishes, makes its appearance." 



It was only on the day before my departure for the congress at 

 Cambridge that I became acquainted with a short note of Prof 

 Seeley, published two years ago in the Proceedings of the Royal 

 Society for 1896 and reprinted in the Annals a^td Magazine of 

 Natural History, Sen 6, Vol. xvii.. No. 98, p. 183, and entitled : 

 " On the complete skeleton of an Anomodont Reptile (Aristo- 

 desmus rlitimeyeri, Wiedersheim) from the Bunter Sandstone of 

 Reihen, near Basel, giving new evidence of the relation of the 

 Anomodontia to the Monotremata." This note ends with the 

 following conclusion : 



" The author argues that the points of structure are so few in 

 which Monotreme Mammals make a closer approximation to the 

 higher Mammals than is seen in this fossil and other Anomodontia 

 that the Monotreme resemblances to fossil Reptiles become increased 

 in importance. He believes that a group Theropsida might be 

 made to include Monotremata and Anomodontia, the principal 

 differences (other than those of the skull) being that Monotremes 

 preserve the marsupial bones, the atlas vertebra, and certain cranial 

 sutures. OrnitlwrhyncJins shows prefrontal and postfrontal bones, 

 and has the molar arch formed as in AnomodontsT 



As however till the present moment the publication of this note 

 has not yet been followed by that of the paper in full, and therefore 

 this important feature in the Monotreme skull has generally 

 remained unnoticed in the scientific world, I deemed it very 

 desirable to bring my observations before the audience of this con- 

 gress. In doing so, I am happy to meet with Mr Seeley's kind 

 approval, and of course fully acknowledge his priority as well in the 

 observation of the fact as in the interpretation of its possible phylo- 

 genetic value. 



In connection with this observation, three questions arise, point- 

 ing to three different lines of investigation, which must necessarily 

 be worked out, before coming to any final conclusion concerning 

 the real importance of the perforation in the temporal region and 

 its bearing on phylogenetic questions. 



In the first place it is absolutely necessary to come to a clear 

 and unequivocal understanding as to the exact homologies and the 

 best nomenclature of the bones composing the temporal region and 

 surrounding the canal in question. 



Secondly, it is desirable to get a full knowledge of the soft parts 

 that occupy this canal, and thirdly to search for similar passages in 

 the temporal region of other animals, especially Mammals. 



I I — 2 



