RECORDS 55 



SECTION OF BIOLOGY. 



Section met at 8:15 P. M., Professor Bashford Dean presiding. 

 The minutes of the last meeting were read and approved. 

 The following program was offered : 

 J. H. McGregor, The Ancestry of the Ichthyosauria. 

 A. G. Mayer, Color Patterns in Lepidoptera. 

 C. C. Trowbridge, The Function of Interlocked Emargi- 

 nate Primaries in Soaring Flight. 



Summary of Papers. 



Dr. McGregor accepted Baur's view that the Ichthyosauria 

 are derived from Permian Rhynchocephalia, but stated that in 

 a study of the Belodontia he had found new evidence as to the 

 nature of the intermediate forms. The latter group is of un- 

 doubted Rhynchocephalian origin, and may almost be con- 

 sidered as a subdivision including forms modified for aquatic life. 

 A comparison of Belodonts and Ichthyosaurs shows that both 

 have evolved in the same direction, though modification has 

 proceeded further in the Ichthyosaurs, which were marine in 

 habit. Almost all of the skeletal features of the two orders are 

 reducible to a common type, and, although not directly ances- 

 tral, the Belodonts must be considered as standing very near 

 the line of descent of the Ichthyosaurs ; the two orders prob- 

 ably had as a common ancestor some aquatic Rhynchocephalian 

 of the upper Permian or lower Trias. The Ichthyosauria are 

 thus brought into relation with the Archosaurian branch of the 

 Reptilia. 



Dr. Mayer presented the results of his study of the color 

 patterns of 1,173 species of lepidoptera: 453 Papilio, 30 Orni- 

 thoptera, 643 Hesperidje, and 47 Castina. Counting sexual 

 differences, 1,340 individual insects were examined ; 542 Papilio, 

 59 Ornithoptera, 688 Hesperidae, and 51 Castina. The num- 

 ber of rows of spots, bands, or combination markings upon the 

 wings were counted, and as well the number of spots in each 

 individual row, and the number of interspaces over which each 



