Mr. E. Lydekker on Nototherium and Zygomatiirus. 261 



cism ; it has relieved me of a foolish fear that, in spite of 

 improbability, the British Museum might possess some posi- 

 tive evidence in natural association of parts that Zygomaturus 

 is Nototherium. I am comforted to find that the hypothesis 

 remains in its pristine purity, also to think that if no better 

 attack upon my position can be made than that which I have 

 met it is pretty secure. An utter failure to show that the 

 right tooth is not the ^li proper to the skull, together with 

 the confession that it is not the premolar of Nototherium, 

 might well have released me from any obligation to cut Mr. 

 Lydekker's Gordian knot. 



Queensland Museum, 

 April 15, 1889. 



XXXI. — Note on the Above. By R. Lydekker. 



Being extremely unwilling to enter into any prolonged con- 

 troversy on this or any other subject, my remarks on the 

 foregoing communication will be of the briefest nature. 



If the author be right in his contention that the lirst cheek- 

 tooth on the right side of the cranium to which the name 

 Zygoniatarus was applied is homologous with and similar to 

 the corresponding tooth on the left, then there may be evi- 

 dence that this skull is specifically distinct from the form to 

 which Sir R. Owen gave the name of Nototherium inerme. 

 This, however, would be very far from proving that these 

 two forms are widely different and have a totally distinct 

 type of appendicular skeleton. Moreover, if it be assumed 

 that the so-called Zygomaturus is widely different from that 

 type of cranium to which the author would restrict the term 

 Nototherium, we are confronted with the difiiculty that while, 

 with one exception, all the complete maxilla? in the British 

 Museum appear referable to Nototherium, all the mandibles 

 seem to be of the type of Zygomaturus. 



In conclusion, I cannot pass over the author's extraordinary 

 statement that the milk-teeth of Marsupials are always similar 

 in structure to their successors, when, as is well known, pre- 

 cisely the reverse is the case. Thus we have only to cite the 

 case of many of the Kangaroos, where a molariform """• ^ is 

 succeeded by a secant SULJ. This ignorance of such a well- 

 known feature among existing forms is not calculated to raise 

 one's estimation of the author's acumen when he has to face 

 the more difficult question of the structure and affinities of 

 extinct types. 



