I'LATK XVIII. 



Pig*. 

 [XOCSRAMtri umhonatuh M. «V II HI 



Fig, 1. DOTSft] view of :l rant of u left valve ndiicod in h'i/.c (ftftei M«-.«ik). 



2. Anterior view of a, eaut of a left valve,, retaining portioni of the 

 libroiiH layer of hIm-11 in the umbonftl region (alter Meek). 



228 



