244 



NATURAL HISTORY BULLETIN. 



Zoanthus, nor did it seem to be covered by a sub-epidermal 

 layer of mesogloea. 



The upper part of each polyp showed a number of ridges 

 radiating, in the completely contracted specimens, from the 

 center of the upper surface of the column; they were not, 

 however, very distinctly marked. The mouth is small and 

 oval or slit-like in form and the stomatodasum presents the 

 usual single siphonoglyph, whose mesogloea is thickened and 

 has the truncate form noted for other species of Palythoa. 



Sections show that the mesenteries are arranged on the 

 brachycnemic plan; I counted in one specimen eighteen pairs 

 and in another twenty. The individual mesenteries are very 

 thin, and each is provided with elongated basal lacuna, which 

 in the lower part of the column becomes almost circular. I 

 can say nothing regarding the musculature of the mesenteries, 

 the internal parts being in a very imperfect state of preserva- 

 tion; I should judge, however, that the longitudinal muscula- 

 ture was very weak as I could find no traces of mesogloeal 

 processes for its support. Reproductive organs, spermatozoa, 

 occurred very abundantly in the lower portions of the mesen- 

 teries and the species seems to be unisexual; in fact all the 

 individuals of a colony seem to be of the same sex, since speci- 

 mens taken from various parts of one colony all possess only 

 spermatozoa. 



The sphincter muscle is moderately long but narrow, con- 

 sisting practically of but a single row of cavities (PI. in, Fig. 

 7). It is, of course, mesogloeal. 



In its general appearance this species resembles the P. 

 mammillosa of Duchassaing and Michelotti as represented in 

 their PI. vi, Fig. 10 ('64), but it must be observed that they 

 include P. ocellata and P. jiava under this title, an alliance 

 which may possibly be correct for P. Jiava, but not, I believe, 

 for P. ocellata. The present species differs from the figure 

 of P. mammillosa given by Ellis and Solander ("86) in that 

 the polyps at the edge of the colony are not at all, or but 

 slightly, separated by longitudinal grooves, a fact which may 

 or may not be of importance, and apparently P. mammillosa 



