148 Mr. G. Kreift on the Dentition o/Thylacoleo carnifex. 



The above notes were taken from living specimens. 



It would be interesting to know more than is known at pre- 

 sent about the distribution of the British Ephemeridse. In 

 Dorset and on Dartmoor Potamanthus erythrophthalmus is the 

 commonest of the genus, whilst P. marginatus is the most fre- 

 quent in the Cambridge district. On the Dart Baetis montana 

 predominates, but B. lutea at Little Bridy, Dorset. At this last 

 place, too, Cloeon Bhodani outnumbers C. bioculatum ; but at 

 Blandford, in the same county, and at Cambridge the converse 

 obtains. From this it would appear that P. erythrophthalmus 

 and C. Bhodani are better fitted to inhabit swift streams than 

 P. marginatus and C. bioculatum. 



XXV. — On the Dentition o/Thylacoleo carnifex {Ow'.). 



By Gerard Krefft. 



[Plate XI.] 



To the Editors of the Annals and Magazine of Natural History. 



Gentlemen, 



In the December Number of your Journal you figure a tooth 

 which is supposed by Prof. M'Coy to be the hitherto unknown 

 canine of Thylacoleo carnifex, because it was discovered " with 

 part of the lower jaw and teeth of Nototherium Mitchellii, on 

 which it had probably been feeding." I do not think the find- 

 ing of such a tooth in proximity with a Nototherium' s teeth is 

 sufficient proof that it belonged to a Thylacoleo, the more so as 

 the huge canine of that animal had never been known before — 

 and never will be known, because the Thylacoleo carnifex was 

 not furnished with canine teeth, and the dental series (in the 

 lower jaw at least) ended in a pair of incisors, from which fact 

 I venture to conclude (guided by the analogy furnished by the 

 dentition of our living Marsupials with two lower incisors, the 

 wombat excepted) that the upper jaw contained the usual six 

 incisor teeth, and that if it ever possessed a canine it must 

 have been a very small one, corresponding to the diminished 

 tooth found in Hypsiprymnus and Phalangista. 



The tooth described by Prof. M'Coy is not referable to Thy- 

 lacoleo ; and the shape of its crown proves it at once to be an 

 incisor, not a canine, and most likely the (incisor) tooth of the 

 animal with the remains of which it was discovered. Prof. Owen 

 (who long ago expressed his opinion to the efi'ect that the dental 

 series of the lower jaw of Thylacoleo would probably end in a 

 pair of incisors) has given us a full description of the teeth of 

 this animal, to which I have nothing to add, except that, with 

 the scanty material at my disposal, I have ventured to recon- 



