RECORDS OF MEETINGS 405 



atrophy of the posterior border of the squamosal would have greatly in- 

 creased the mobility of the quadrate. 



Paleontological and embryological evidence showed that the existing 

 joint between the skull and the lower jaws in mammals is a neomorph, 

 probably developed pari passu with the atrophy of the quadrate and 

 articular bones. The application of Reichert's theory to the Theriodontia 

 required only that the vestigial quadrate should be freed from its squa- 

 mosal socket, and secondly that it and the articular should be brought 

 into contact with the stapes or primary auditory rod. But how can we 

 conceive an adaptive, mechanical motive for this extraordinary change? 

 Such seems to be furnished by the embryology of the tympanic chamber 

 of mammals. As is well known, this chamber appears below the ossicles 

 as a diverticulum of the first gill opening. It grows upward and em- 

 braces the ossicles, which finally appear to be inside the cavity but are 

 morphologically outside of it, since they never pierce its epithelium. So 

 in the hypothetical pro-mammal the vestigial quadrate and articular on 

 the one hand and the stapedial rod on the other may have been embraced 

 by the up-growing tympanic sack or chamber and finally pressed into con- 

 tact with each other. The vestigial jaw elements may thus have come to 

 share in the vibrations of the chamber and of the stapes, and thus was 

 initiated their career as accessory auditory ossicles. A somewhat analo- 

 gous case is the transformation in siluroid fishes of certain vertebral ap- 

 pendages into a chain of ossicles for transmitting vibrations from the air 

 bladder to the internal ear. 



Mr. Gregory^s paper was illustrated with lantern slides. 



The Section then adjourned. 



L. HUSSAKOF, 



Secretary. 



SECTION OF ASTRONOMY, PHYSICS AND CHEMISTRY. 



February 21, 1910. 



By permission of the Council, no meeting was held. 



Edward J. Thatcher, 



Secretary. 



SECTION OF ANTHROPOLOGY AND PSYCHOLOGY. 



February 28, 1910. 



Section met at 8 :15 p. m., in conjunction with the New York Branch 

 of the American Psychological Association, at the American Museum of 

 Natural History. 



