RECORDS. 447 



Professor Osborn showed that the speculation of recent au- 

 thors (Cope, Baur, Osborn) regarding the ancestry of the mam- 

 maha turns back to certain Permian reptiles of the orders Therio- 

 dontia Owen, and Gomphodontia Seeley. He reviewed the 

 characters of the skeleton of these Theriodontia, showing their 

 unmistakable promammalian features. A number of persistent 

 reptilian characters were also cited. In conclusion, the speaker 

 said that these Theriodontia have the geological age required for 

 ancestors of the mammalia, and are the only type of reptiles 

 which exhibit mammalian affinities. Their great size and cer- 

 tain adaptive specializations alone bar any known type from di- 

 rect ancestry of the much smaller earliest mammals ; but this 

 fact does not preclude the existence of very small unspecialized 

 forms which may have developed into the mammalian type. Pro- 

 fessor Osborn's paper was illustrated by lantern slides. 



Dr. Chapman described the various types of vegetation and 

 the altitudinal distribution of birds along the course of the two 

 railroads running from the coast at Vera Cruz into the table- 

 lands of the interior. His paper was also illustrated by lantern 

 slides. In answer to Professor Britton's question w^hether the 

 variations in air pressure have any influence in modifying bird 

 structure, the speaker said apparently not. They undergo dif- 

 ferent pressure, as shown by height of flight, and seem to thrive 

 equally well under differing conditions of barometric pressure. 



Professor Lloyd showed that scales which subtend the fasci- 

 cles oi Pinus ponderosa are morphologically equivalent to leaves ; 

 and, when hypertrophied, these leaves closely resemble the leaf 

 of the genus Pseudotsuga. The speaker suggested that the 

 Pines may have been derived phylogenetically from a general- 

 ized form represented by Psaidotsuga, and that the hypertro- 

 phied leaves are atavistic. 



Gary N. Calkins, 

 Secretary of Section. 



