256 



SCIENCE. 



[N. S. Vol. XIX. No. 476. 



and ulna actually cross each other, al- 

 though as in the Proboseidea this crossing 

 is much less apparent, owing to the great 

 proximal expansion of the ulna. 



On the Use of the Sandblast in Cleaning 

 Fossils: Henry Fairfield Osborn. 

 The introduction of the compressed air 

 chisel by the Field Columbian Museum has 

 greatly reduced the cost of removing rock 

 from fossils. This chisel has been intro- 

 duced also in the National Museum with 

 success. For larger masses of rock it an- 

 swers every purpose. The writer has re- 

 cently been experimenting with a sand- 

 blast, driven by a compressed air engine, 

 with admirable results. This method is 

 peculiarly adapted to the finer work. It 

 should be used under fifty-pound pressure, 

 with tubes of fine diameter. Although not 

 thoroughly tested as yet it promises to give 

 remarkable results both in cleaning surfaces 

 and in removing the matrix in the cavities 

 of small skulls. Combined with the com- 

 pressed air chisel it will probably reduce 

 the cost of preparing fossils to one third of 

 that involved by the use of hand tools. 



Conclusive Paleontological Evidence for the 

 Tritubercular Theory: Henry Fairfield 

 Osborn. 



That part of the tritubercular theory 

 which homologizes the cusps composing the 

 main triangle in the upper and lower 

 grinding teeth of mammals, has been seri- 

 ously questioned of late; first, because it 

 does not accord with all the embryologieal 

 evidence, second, because the superior pre- 

 molar teeth appear to afford a demonstra- 

 tion that the upper molar teeth evolved in 

 a manner which was subsequently pursued 

 by the premolars. The tritubercular the- 

 ory has been steadily losing ground; some 

 authors have recommended that the cusp 

 homologies and terminology be totally 

 abandoned. A fresh investigation of the 



paleontological material available has, how- 

 ever, demonstrated beyond question the 

 truth of the theory in its original form. 



The superior molars of Triconodon and 

 of Peralestes in the British Museum sup- 

 port the original view that the cusp (pro- 

 tocone) homologous with the reptilian cone 

 is internal or lingual in position. Through 

 the kindness of Professor Charles E. Beech- 

 er, the superior molar teeth of the Jurassic 

 Dryolestes in the Tale Museum have been 

 reexamined, and are found to correspond 

 exactly both with the original description 

 of Marsh and with the conditions set forth 

 in the original tritubercular theory. The 

 main cusp, or protocone, is internal and 

 supported on a stout fang; the secondary 

 cusps, representing the para- and meta- 

 cones, are external and supported on lesser 

 fangs. This evidence, together with that 

 deduced from comparative anatomy and 

 paleontology, establishes the tritubercular 

 theory beyond further question. 



A Reclassification of the Beptilia: Henry 



Fairfield Osborn. 



The Reptilia are divided into two sub- 

 classes: (1) Synapsida, including the Co- 

 tylosauria^ Anomodontia, Sauropterygia 

 and Testudinata. The Anomodontia are 

 divided into the Therocephalia (Broom), 

 the Theriodontia (Cynodontia Owen), 

 the Dieynodontia, representing progressive 

 phases of evolution of the skull and spe- 

 cialization of the teeth. Of these the 

 Theriodontia stand nearest the Mammalia. 

 (2) Diapsida, embracing the new super- 

 order Diaptosauria, Avhich includes the 

 seven orders and suborders Procolophonia, 

 Protorosauria, Proganosauria, Gnathodon- 

 tia, Choristodera, Pelycosauria and Rhyn- 

 chocephalia. The remaining Diapsidan 

 orders are the Parasuehia (=Phyto- 

 sauria), Ichthyopterygia, Crocodilia, super- 

 order Dinosauria, superorder Squamata 

 and the order Pterosauria. Birds sprang 



