2 A2 NATURAL HISTORY BULLETIN. 



ORDER ZOANTHE£. 



Family ZOANTHID.-E. 



9. ZOANTHUS SOCIATUS Ellis. 



Dry Tortugas; 2 colonies. 

 Spanish Wells; 3 colonies. 



I have compared these specimens with Z. sociatus from the 

 Bahama Islands and can rind no differences sufficient for their 

 separation. All the colonies were adherent to blocks of coral 

 rock somewhat uneven in shape, and, as a result, there is 

 some difference in the size of the various individuals, since 

 there seems to be a tendency for the disks of the expanded 

 polyps to lie at approximately the same level. Those indi- 

 viduals which are situated in the depressions, or on the sides 

 of a block, consequently grow to a greater height than those 

 situated on elevations or on the general level. Thus in one of 

 the colonies examined many of the individuals measured only 

 0.5 cm. in height, while others measured as much as 2 cm., 

 these measurements being in both cases of individuals whose 

 diameter slightly below the apex of the contracted column 

 was about 0.5 cm. There were of course numerous small 

 polyps recently budded off from the stolons, whose height was 

 less than that given for the small adults, but these could be 

 readily recognized by their small diameter. 



I can add nothing to the description of Z. sociatus I have 

 already published ('89), especially since the internal parts of 

 the specimens examined were rather badly macerated. I give, 

 however, in PL 111. Fig. 1, a view of a transverse section of 

 the sphincter, having omitted such a figure in my earlier paper. 



10. Palythoa nigricans sp. nov. 



Station No. 24. Off Key West; Sand Key light bearing 

 N. N.W., Key West light bearing N.; about 60 fathoms; 

 3 colonies on coral rock. 



I have adopted for the Zoanthese the generic definitions as 



