688 Reports on the Zoological Collections made in Torres Straits, 1888-1889. 



Gemmaria macmurrichi, n. sp. 



(PL LSI., fig-. 11 ; PI. Lxiii., fig. 7.) 



Form. — Erect, rigid, wider above than below; upper portion of contracted 

 specimen with minute radiating corrugations. 



Colour. — Sandy. 



Dimensions. — Height, 13 mm.; diameter, 3"5 mm. above, 2 mm. below. 



Locality.- — Channel between Mer and Dauar, Murray Islands. 20 fathoms. 

 Mar. 16, 1889. One specimen only. 



Body-wall (PL lxiii., fig. 7). — The ectoderm is discontinuous, being broken 

 up by thick, irregular strands of mesogloea, which unite to form a distinct peri- 

 pheral layer lying beneath the cuticle. The ectodermal cells are for the most 

 part disintegrated in our specimen, their contents adhering to the surrounding 

 mesogloea and leaving an empty space in the centre. The incrustations consist 

 chiefly of coarse grains of calcareous sand, but a few silicious sponge spicules are 

 also present, and are left after decalcification. Beneath the incrustations lies an 

 encircling sinus, which is, however, so much interrupted by the mesogloea as to 

 appear in horizontal section as a circular series of lacunae, each lacuna lying imme- 

 diately below the union of a mesentery with the body- wall, two or three lacunse 

 being occasionally united by a fine canal. As the base of the polyps is approached 

 the lacunse gradually become smaller and finally disappear. It thus appears that 

 the body-wall is pierced by a number of canals, which run vertically upwards from 

 near the base to the disc of the polyps ; these canals being occasionally connected 

 with each other by much finer crossing canals. Similar fine canals are occasionally 

 to be found running from the vertical canals outwards towards the ectoderm. Cell 

 islets are scattered abundantly through the mesogloea, as also are single cells 

 elongated into delicate fibrils connected both with endodorm and mesogloea, such as 

 we have described in other species of Zoanthese. Large lacunse, densely filled with 

 deeply staining granules, are numerous at the base of the polyp. These are clearly 

 connected with the mesenterial canals which arise in this region. They seem to 

 be of ectodermal origin. The endoderm which lines the column is not very well 

 preserved, but it appears to form a regular layer of medium thickness. The 

 muscular layer is well developed in the ujaper part of the column. Lower down it 

 is weaker. 



Sphincter muscle. — The sphinctermuscleissingle,mesogloeal,and is well developed. 



Disc and tentacles. — Unlike the two species of Gemmaria described by M'^Murrich, 

 the ectoderm of the disc and tentacles contains no zooxanthellse, nor have we ob- 

 served them in the endoderm either. The ectodermal muscular layer is fairly 



