16 On Two New Genera of Polyzoa. 



tubercle on each side for the attachment of the operculum. 

 Above the mouth on each side is a thick, rigid, vertically- 

 grooved process, usually of a brown or purplish colour. 

 These are so arranged that the spine on one side is further 

 forward than the corresponding one of the next cell on that 

 side, while the opposite spine is posterior to the correspond- 

 ing one of the adjacent cell. The posterior half of the cell 

 forms a lofty convex or ridged elevation, the surface of 

 which is finely granular. Along each margin on the summit 

 is a flattened, semipyriform, bullate process, the rounded 

 surface being turned towards the inside of the cell. On one 

 side the thick end is posterior, the pointed extremity being 

 continuous with the raised margin; while on the other side 

 the arrangement is reversed, the rounded extremity being 

 anterior. A short distance behind the mouth the calcareous 

 matter is deficient, leaving a space extending the whole 

 width of the cell entirely membranous. The avicularia 

 are of two sorts. The usual form has a large triangular 

 mandible directed forward, is situated at the base of 

 one of the small cells at a bifurcation of a series, and occu- 

 pies the cell to the top of the elevation. The other, of 

 which I have only seen a single example, occupies the whole 

 width of two cells at a bifurcation, and has a broad, shallow 

 mandible, hollowed in the middle. 



Locality. — Queenscliff ; Portland, Mr. Maplestone. 



The regular transverse arrangement of the cells, the raised 

 continuous posterior parts with the bullate processes, and the 

 dark colour of the large, prominent, grooved, oral spines 

 render this one of the most beautiful of the polyzoa. 

 When broken, the fracture takes place through the mem- 

 branous part of the cells, so that a detached row may 

 consist of the anterior and posterior halves of the cells of 

 two distinct transverse series. 



Family DIASTOPORIDjE. 



Genus Densipora. 



Polyzoary forming an encrusting mass, discoid when 

 young, composed of numerous long, closely-packed, tubular 

 cells, continuous throughout the whole thickness, and with 

 the orifices not projecting. 



