RECORDS OF MEETINGS OF 1909. 
299 
The sixth stage may be reconstructed by a comparative study of the 
Eocene Creodonts and the Tertiary and modern Insectivores, by subtracting 
from each known family its well marked lines of specialization, thus leaving 
a residue of primitive mammalian characters. This generalized Placental 
type may have attained its distinctive features in the Jurassic or Cretaceous. 
From the contemporary Marsupials it was separated by the retention of a 
complete milk dentition and by certain details of the skull. In general 
form and proportions it may have resembled the above mentioned Marsu¬ 
pial Marmosa, especially in the skull, but in the skeleton it approximated 
rather towards the earliest Eocene Creodonts and Insectivores and, in many 
characters, towards the modern Tree Shrews ( Tupaiidoe ). From such a 
generalized Cretaceous Insectivore-Creodont type all the other orders of 
Placentals may have been directly or indirectly derived, but the details of 
this great adaptive radiation must be reserved for another occasion. 
Mr. Morse showed a series of slides illustrating the Harpswell region 
and environs. The laboratory was founded by Dr. J. S. Kingsley in 1898 
in the little fishing village of South Harpswell, Maine, eighteen miles from 
Portland. The immediate region is rich in interesting forms of animal and 
plant life which are peculiarly adapted to the use of investigators. The old 
Tide-mill collecting ground and samples of some of the more important 
animals and plants to be found there were illustrated. The geology of the 
Harpswell region has not been worked up and this presents interesting 
questions, especially in glacial geology. The speaker pointed out the 
advantages offered by the laboratory over those of our other marine stations. 
Professor Grabau said, in abstract: Paleozoic corals show in their septal 
development a fundamental tetrameral plan. This is persistent in the 
earliest known forms but becomes masked in later species by the secondary 
assumption of radiality. The development of the mesenteries in modern 
Hexacoralla shows a similar order of appearance. Pairs of mesenteries 
develop in succession in bilateral disposition. From the position of the 
muscle strands they are either dorsads (musculature turned dorsal-ward), 
or ventrads. The first and second pairs are ventrads. The third (ventral 
directive) is a pair of dorsads, the fourth (dorsal directive) is a pair of 
ventrads. The fifth and sixth pairs are dorsads forming with the first and 
second pairs four false pairs of “braces.” After that the mesenteries appear 
in compound pairs, a pair of dorsads and one of ventrads appearing simul¬ 
taneously. Thus in the corresponding inter-mesenterial spaces a brace of 
new mesenteries appears, the order being comparable even in detail to the 
order of appearance of the septa in the Paleozoic Tetracoralla. 
The Section then adjourned. 
L. Hussakof, 
Secretary. 
