122 PROCEEDINGS OF THE ACADEMY OF [1889. 



zooxanthellse. I have found this peculiar structure of the disc 

 ectoderm in no other Zoanthids. Unfortunately the preservation of 

 the specimens was not sufficiently good to allow of the histological 

 details being studied. The gonidial groove of the stomatodamm is 

 rather broad and the mesogloea lining is thickened and truncated 

 upon the endodermal side, the macrodirectives being inserted into 

 each angle of the truncation. 



The mesenteries are arranged on the microtypus, there being 

 about twenty-six pairs. The basal canal is large, and contains 

 foreign particles similar to those found in the lacunae of the column, 

 The mesogloea is thickened towards the base of the mesenteries and 

 contains in addition to the basal canal, several others nearly circular 

 in section and completely filled with spherical granular cells. 

 The endoderm throughout contains zooxanthelke. No reproductive 

 organs were present. 



9. Corticifera glareola, Les. 



Synon.: Corticifera glareola. Lesueur. 1817. 



Palythoa glareola. Milne-Edwards. 1857. 



The identification of this form depends mainly on the coloration, 

 which Professor Heilprin informs me is sufficiently similar to Les- 

 ueur's description. 



The polyps form encrusting masses, and are so deeply imbedded 

 in the coeneuchyme, that in contraction a slight depression alone 

 indicates the position of the various individuals, or in some cases a 

 slight annular elevation. The species is by this peculiarity readily 

 distinguishable from C. ocellata, as well as from C. jiava of the 

 Bahamas, which stands in an intermediate position as far as the pro- 

 jection of the polyps above the ccenenchyme is concerned. The 

 form described from the Bermudas by Erdmann, and named C- 

 lutea by Hertwig resembles C. glareola in this respect, but appears 

 to differ from it in other points. 



The mesogloea is, with the exception of a narrow band immediately 

 adjoining the endoderm of the polyps, richly supplied with imbedded 

 foreign bodies, so that the entire colony is very hard, almost stony 

 in its consistency. C. ocellata is much less richly provided with 

 foreign particles, and the same is the case with Hertwig's C. latea. 

 Whether this is a characteristic of sufficient importance for specific 

 distinction can only be ascertained by the examination of numerous 

 specimens of some species, obtained from different localities and 

 living under different conditions. In fact our knowledge of the his- 



