PLATE 12. 



FiS- 1. Roconst ruction of interior end of Strophonienia scandens. 



Fiff. "2. Section through dor.so-terminal sense organ of Alexandromenia valida. 



I''ifl. i!. Ixceonst ruction of (losterior cud of Stroi)honu'nia .si)ino.sa, small specimen. 



Fig. 1. Reconstruction of iiosterior end of C'haetoderma attenuata, showing principal nerves, two 

 (brn) ]);issing into the gill. 



Fig. 5. Reconstruction of anterior i>arl of nervo\is system of Alexandromenia agassizi. 



Fig. I). Same of ])oslerior end. 



