5()S PEHCIVAL HAILKV 



to represent as accui-ately as possible the phylogenetic stages of 

 greatest value: 



Ainphioxus 



Cyclostoines 



Selachians 



Ganoids 



Urodeles (for Stegocephali) 



Chelonia (for Theromorphs) 



Monotremes (for Pantatheria) 



Marsupials (for primitive Insectivora) 



Insectivora 



Lemurs (modern Mesodonta) 



Cercopithecoidae (tailed moniveys of Old World) 



Tailless Apes (Gorilla, etc.) 



Pithecanthropus (extinct) 



Homo primigenius (extinct) 



Homo sapiens 



Below the Urodeles, the lateral telencephalic choroid plexus 

 is very rudimentary if it appears at all. Its condition in the 

 Urodeles has been thoroughly elucidated by Warren's ('05) ac- 

 count of Necturus maculatus. For the Chelonia, Chrysemys 

 marginata was selected because it was readily accessible and also 

 because a great part of the work had already been admirably 

 done by Warren ('11) in the course of his investigation of the 

 ''Paraphysis and Pineal Region in Reptilia." It stands a little 

 closer to the line of ascent of the mammals than the hzard, 

 Platydactylus mauritanicus, described by Tandler and Kantor. 

 Of the forms above the Chelonia, only Didelphys virgin iana 

 representing the Marsupials, was available. The present com- 

 munication is concerned with Chrysemys marginata and a review 

 of the literature, leaving Didelphys for a later paper. 



HISTORY 



There are no choroid plexuses in Amphioxus (Burckhardt, '94). 



Ahlborn ('83) describes well developed plexuses in the roof of 

 the hindbrain of Petromyzon planeri, and also in the roof of the 

 midbrain. The plexus of the diencephalic roof is not so well 

 developed and no reference is made to any telencephalic plexuses. 

 Burckhardt ('94) writes of Petromyzon fluviatihs: 



