EXPLANATION OF PLATE XXXVII. 



Figure 275. — Zygodactyla Grcenlandica, (p. 729 ;) profile view, one-lialf natural size. 

 276. — Bougainvillia superciliaris, (p. 733;) a branch, much enlarged. 

 277. — Pennaria tiarella, (p. 735;) a branch, natural size. 

 278. — The same; one of the hydroids, with medusse, buds developing at the 



base of the proboscis. 

 279. — Sertularia pumila, (p. 732 ; part of a colony on a frond of sea- weed, 



natural size. 

 280. — Sertularia argentea, (p. 7.32;) a branch bearing reproductive capsules, 



(gonothecse,) with the soft parts removed, much enlarged. 

 281. — Obelia commissnralis, (p. 728;) a branch bearing hydroids and one 



female gonotheca, much enlarged. 



(Figures 275 and 279 were copied from A. Agassiz ; 276 and 281 from L. Agassiz ; 278 from J. Leidy ; 

 7 and 280 were drawn by A. E. YerriU.) 



