October 12, 1900.] 



SCIENCE. 



559 



The inflection very early became fixed in 

 the Marsupialia, as shown by the Jurassic 

 forms Spalacotherium, Phascolotherium, and 

 Trlconodon. In the opossums (Didelphy- 

 idse), which (excepting Myrmecobius) are 

 the most primitive forms of to-day, the in- 

 flection exhibits a primary relation to the 

 vertically acting non-sectorial teeth. The 

 same may be said of the Dasyuridse judging 

 from Dasyurus. The thylacine, representing 

 a predaceous carnivorous type, has not been 

 available for examination. The kangaroos 

 (Macropodidse), which resemble the pla- 

 cental Ungulata, to a great extent, in 

 tooth action and jaw structure, show no 

 downward prolongation of the angle for the 

 increase of the pterygoid insertion area 

 such as is characteristic of the latter. The 

 presence of the inflection makes it necessary 

 to get the required increase in another way, 

 and in such a manner as to substitute a 

 transverse action of the muscle for a primi- 

 tively vertical one. It is accomplished by 

 a great excavation of the internal surface of 

 the base of the inflected angle. In its in- 

 terference with the downward prolongation 

 of the angle, the inflection is detrimental ; 

 in other respects it is functional, since that 

 part of the pterygoideus internus which is 

 attached to its tip still acts vertically and 

 also opposes the traction of the masseter on 

 a weak symphysis. The phalangers (Pha- 

 langeridse) take an intermediate position 

 between the Didelphyidse and the Macropo- 

 didse. Tarsipes, which is unique in lacking 

 the inflection, is degenerate in this respect, 

 since it also lacks the coronoid process and 

 has reduced teeth. The koala (Phascola- 

 rdus) shows a secondary straightening out 

 of the angle associated with a deep auditory 

 bulla. The wombats (Phascolomyidge), and 

 the bandicoots (Peramelidse) show no points 

 of special interest. 



An examination of the available evidence 

 leads to the following conclusions : 



(1) The inflection of the angle is primar- 



ily associated with an exclusively vertical 

 action of the teeth. 



(2) It probably originated by a reduc- 

 tion of bony elements and of Meckel's car- 

 tilage on the inside of the jaw. 



(3) The inflection became fixed in the 

 Marsupialia, and is to be regarded through- 

 out the existing series as a persistent prim- 

 itive character. 



(4) In primitive Marsupials, such as the 

 Didelphyidse, the inflection retains its orig- 

 inal character, while in specialized types, 

 such as the Maci'opodidas, it becomes modi- 

 fied in an attempt to substitute a partly 

 transverse muscular action for an exclu- 

 sively vertical one. 



(5) The inflection may be secondarily 

 functional in many cases in opposing the 

 traction of the pterygoideus internus to the 

 lateral traction of the masseter on a weak 

 symphysis. 



B. Aethub Benslet. 

 Columbia Univeesity. 



OKLAHOMA GEOLOGICAL SURVEY. 



The necessity for geological work in 

 Oklahoma is the more obvious in view of 

 the fact that the surveys of adjoining States 

 have been in progress for a number of years. 

 Kansas, Missouri, Arkansas and Texas have 

 already published largely on this subject, 

 while in Oklahoma nothing has been written 

 except a few scattered articles. 



During the past summer the initial work 

 of the Survey has been accomplished. A 

 sum sufiBcient to begin the work was appro- 

 priated by the last Legislature. Dr. A. H. 

 Van Vleet, of the University of Oklahoma, 

 had charge of the work and acted as zoolo- 

 gist for the Survey. Other members were 

 C. N. Gould, geologist, Paul J. White, 

 botanist, and Roy Hadsell, general assist- 

 ant. The party traveled by wagon, being 

 provided with tents and other necessary 

 camping facilities. 



It had been planned to spend part of the 



