EXPLANATION OF PLATE XXXVII. 
Figure 275.—Zygodactyla Groonlandica, (p. 729 ;) profile view, one-half 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 meduse, buds developing at the 
base of the proboscis. 
279.—Sertularia pumila, (p. 7323) part of a colony on a frond of sea-weed 
natural size. 
280.—Sertularia argentea, (p. 732;) a branch bearing reproductive capsules 
(gonothecz,) with the soft parts removed, much enlarged. 
281.—Obelia commissuralis, (p. 728;) a branch bearing hydroidgs and one 
female gonotheca, much enlarged. 
(Figures 275 and 279 were copied from A. Agassiz; 276 and #31 from L. Agassiz; 278 from J. Leidy ; 
77 and 230 were drawn by A. E. Vervill.) i 
