150 Happon anp DusrpeEN—Some Actiniaria from Australia and other Districts. 
the incrustations, the boundary between the ectoderm and mesogloea is very 
irregular. 
The mesogloea below the cesophageal region is not much thicker than the 
ectoderm, but in that region it thickens considerably. It is irregular in appear- 
ance, due to the numerous incrustations. Small cell-islets occur, but not 
abundantly. The endodermal muscular layer is but feebly developed. 
The endoderm is narrow and the cells uniform in height. 
Sphincter muscle (Pl. vu, fig. 8).—The sphincter muscle is mesogloeal and 
single. It is well developed. At its distal and thickest part, the irregular 
cavities extend almost across the whole diameter of the mesogloea, but lower 
down the spaces gradually become smaller. The muscle fibres are thin, and 
the cavities hollow. 
Dise and Tentacles.—The large dark-coloured nematocysts occur in the ectoderm 
of the tentacles along with vast quantities of another smaller form. The 
ectodermal circular muscle is well developed on the plaitings of the mesogloea. 
The endodermal muscle is only feebly developed. The endoderm is well 
developed. 
Gsophagus.—The ectoderm of the cesophagus is almost smooth, not being 
thrown into well-marked folds. The groove is well developed, and the mesoglea 
thickened in that region. 
Mesenteries.—The arrangement of the mesenteries is macrocnemic. Owing to 
the fact that all the four specimens cut contain well-developed ova, this arrange- 
ment is not always easy to discern. Only in one or two instances can any 
trace of the imperfect mesenteries be seen. 
Gonads—All the four individuals examined contained only ova. 
It is characteristic of certain species of Epizoanthus to be commensal with 
hermit-crabs, and the carcinecia which are thus formed may simply incrust 
the shell of the Gastropod, or they may actually replace it with their own 
coenenchyme. 
Our species may be readily distinguished from the others which form 
carcinecia, as the polyps are numerous on the oral aspect of the Gastropod 
(Murex) shell; in other species of Epizoanthus that aspect is either bare of polyps 
(£. incrustatus, D. & K., E. cancrisocius, v. Mart., ef. Studer, &e.), or with one 
ventral polyp, and the remainder marginal (LZ. paguriphilus, Verr., E. parasiticus, 
Hertw.—probably not of Verrill, &c.). 
