RECORDS OF MEETINGS 419 



Summary of Papers. 



Mr. Gregory said in abstract : In 1904, Dr. W. D. Mathew interpreted 

 the characters of many Eocene mammals of various orders as pointing to 

 a common stem form of arboreal habits and structure. The oriental in- 

 sectivore Tupaia and its little known Bornean ally Ptilocercus lowii, 

 serve to illustrate these characters in still living forms. They have a 

 divergent but not yet opposable thumb and great toe, their habits are 

 chiefly arboreal and the diet insectivorous-frugivorous. Tupaia retains 

 many skeletal features that were characteristic of Eocene unguiculates, 

 e. g., long humerus and femur, humerus with entepicondylar foramen, 

 femur with third trochanter, radius and ulna and tibia and fibula sepa- 

 rate, flexible carpus and tarsus, semiplantigrade, five-toed manus and pes 

 with divergent digit I, free central carpi, astragalus without trochlear 

 keels and with a rounded head, vertebral formula C. 7, D. 13, L. 6 or 7, 

 S. 3,Cd. 23-26 — and many others. Other features distinctly foreshadow 

 the primate type, e. g., relatively large brain case, broad forehead, large, 

 posteriorly closed orbits and especially the structural details of the audi- 

 tory bulla and ossicles, dentition and astragalus. In Ptilocercus, the skull 

 and dentition is even more distinctly lemuroid, but the rest of the skele- 

 ton is unknown. It is of course possible that these lemuroid characters- 

 are entirely due to convergent evolution, but the provisional conclusion is 

 that the Tupaiidse are descended from the Insectivore stock that gave rise 

 to the primates. Attention was called to the resemblances between Ptilo- 

 cercus and the lower jaw from the Bridger Eocene described by Matthew 

 as Entomolestes grangeri. The only differences are such as frequently 

 separate more generalized forms from their descendants. 



The paper was illustrated with lantern slides and specimens. 



Professor Crampton gave a brief account of the new results obtained 

 in the course of a journey of seven months' duration among the Society, 

 Cook, New Zealand, Tongan, Samoan, Fiji and Hawaiian Islands. The 

 organisms forming the material of investigations were terrestrial snails 

 of the genus Partula, a strictly Pacific group. The species differ when a 

 comparison is made of forms occurring in neighboring but isolated valleys 

 of one island, in different islands of the same group and in different 

 groups of islands. The uniform principle of distribution summarizing 

 the observed facts is that the degree of geographic proximity of any two 

 comparable regions is correlated with the degree of biological differentia- 

 tion of their species. 



