186 



broad, oblique, rounded quadrangle, and only about the middle third is occupied 

 by the mandibular cavity, which is irregularly vase-shaped and surrounded by 

 a thin, wide marginal expansion. 



The colonies are partly incrusting, partly free, with slender, hollow branches. 

 I have examined a number of colonies of this species from Torres Straits and 

 from Port Denison, Queensland, belonging to the Museum of Zoology at Cam- 

 bridge. 



Thalamoporella falcifera Hincks. 



Steganoporella Rozieri, Form falcifera Hincks, Annals Nat. Hist., ser. 5, 



Vol. VI, 1880, pag. 28—29, PI. XVI, fig. 2. 



(PI. VI b, figs. 6 a— 6 e). 



Length of zocecia 0,53 — 0,66™™- The aperture, the size of which may be 

 contained 3 — 4 times in the whole length of the zocecium, has a broad and deep 

 sinus and parallel or almost parallel lateral margins. The operculum has only 

 a short chitinous sclerite on either side proximally. The clearly defined adoral 

 areas are well developed and have generally small and low acropetal spines, which 

 only take up a small part of their surface. The two opesiular outgrowths gener- 

 ally reach the basal wall, one of them only touching it in an extremely small, 

 closed or open, curved line, while the other meets it in a considerably larger, 

 open, recurved line. The finely tuberculous cryptocyst has widely scattered pores. 



Ooecia are not found. 



The avicularia are rather small with a very well developed, distal cryptocyst 

 and a very narrow, pointed, sabre-like, curved mandible without a marginal ex- 

 pansion, the entire breadth being occupied by the mandibular cavity. 



Of this species, which incrusts algae, I ^ have examined colonies from the Java 

 Sea (Andrea), on Sargassum buxifolium from Campeche Bank, Yucatan on Sar- 

 gassum hystrix (the herbarium of algse in Botanical Museum), on Sargassum sp. 

 from lat. 23" 30' N., long. 40" W. (Andrea) and on Vidalis spiralis from Geo- 

 graph Bay, Australia. 



Thalamoporella Harmeri n. sp. 



(PI. VI c, figs. 1 a— 1 h). 



Length of zooecia 0,53 — 0,57™™ The aperture, the length of which may be 

 contained a little more than 2^2 times in the whole length of the zocecium, has 

 a broad and deep, often trapeziformly rounded sinus. The operculum is attached 

 by two unusually strong hinge-teeth, and the whole of its marginal portion is 

 unusually strongly chitinized, so that its surface shows a marked contrast between 



