On Two New Genera of Polyzoa. 17 



D. corrugata. 



This species forms calcareous masses, more or less sur- 

 rounding the stems of Cymodocea antarctica, varying in 

 length up to about an inch, and in diameter to nearly half 

 an inch. The surface is raised into numerous ridges, 

 variously inosculating, and irregularly surrounding the 

 polyzoary. The summit of these ridges generally forms a 

 raised border, composed of a series of vertical, blunt 

 processes, united side to side, except at the rounded 

 extremities. The usual thickness of the polyzoary 

 from the inner surface is about an eighth of an 

 inch. The cells are very narrow, continuous through- 

 out the whole thickness, and closely united, the walls 

 of the contiguous cells being coalescent and indis^ 

 tinguishable. The interior of the cells is obscurely and 

 irregularly transversely ridged, and is sparsely perforated 

 by minute rounded pores. The orifices are circular or poly- 

 gonal, with several thick calcareous processes from the 

 margin. These are more numerous and larger towards the 

 summits of the ridges, the raised border of which seems to 

 be formed by the peculiar arrangement and union of similar 

 larger processes. The size and shape of the orifices of the 

 cells vary greatly, and between them are frequent smaller 

 pores. The cells are so closely packed and the walls so 

 thin, that the whole surface has a honey-combed appear- 

 ance. 



The examination of full-grown individuals would leave 

 the exact position of this species doubtful, but an inspection 

 of young specimens shows its Diastoporidan characters. The 

 smallest specimen I have is about one-twentieth of an inch in 

 diameter, is discoid, of considerable thickness in the centre, 

 with the cells closely connate, vertical in the middle, and 

 oblique towards the circumference. Among the marginal 

 cells a few small pores are to be seen. The elevated ridges 

 are early developed, and in a specimen an eighth of an inch 

 in diameter are well marked. In completely encircling 

 specimens, the line of coalescence of the margins of the poly- 

 zoary is generally readily discernible by the presence of a 

 tortuous ridge, similar to the other corrugations. 



Locality. — Queenscliff; Portland, Mr. Maplestone; Warr- 

 nambool, Mr. Watts. 



c 



