B. !Ebe isoehelas are t^ically aromte. 
1. The principal splcnles are very thick (over 20 miera) 
and scarcely splned at all tvmm (e) 
2. The principal spicules are entirely spined, 
a. Ahout S fflicra thick, the chelas about 36 micra lindgrenl (f ) 
h. About 15 fflicra thick, the chelas about 24 micrn. .... roosevelti 
