352 



scribed form from Singapore just mentioned, which for the rest is most closely 

 related to P. japonica, we find instead of the scattered pores in P. japonica such 

 a distal pore-chamber in most of the zooecia, and this may sometimes attain a 

 third of the whole length of the zoa>cium. 



Petralia japonica Busk. 



Lepralia japonica Busk, Challenger, Zoology, Vol. X, 1884, Part I, 



Cheilostomata, p. 143, PI. XVII, fig. 5. 



(PI. XVIll, figs. 5 a-b). 



The zooecia quadrangularly or hexagonally tongue-shaped, covered by a 

 yellowish brown membrane and provided both on the frontal and on the basal 

 wall with numerous, scattered pores, between which there are larger and smaller 

 tubercles. The pores of the frontal wall are however considerably larger and as 

 a rule somewhat more numerous than those of the basal wall. The large, some- 

 what elongated aperture, which is provided with a thick, but not very promin- 

 ent peristome, has a slightly concave proximal margin, and each lateral margin 

 is provided in its proximal half with a part projecting inwards, within which 

 there is a stout hinge-tooth. The operculum, which is well-chitinized and dis- 

 tinctly separated from the compensation-sac, has a stronger chitinized marginal 

 ridge, which joins on to a muscular process almost medially on each lateral 

 margin. The proximal margin however has only a continuation of this on each 

 side. Each distal wall is provided with up to 16 and the distal half of each lateral 

 wall with up to 8 multiporous, scattered rosette-plates with 4—7 pores. 



The ocecia, which appear very seldom, have their basal half sunk into fairly 

 deep pits, the base of which is formed by the cryi)tocyst, which is provided with 

 pores, of the distal zooecium. Their frontal surface, which may be more or less 

 strongly arched, is provided with numerous, densely placed, small pores. 



Avicularia. On the one lateral margin of the aperture, in the neighbourhood 

 of the inwardly projecting part, we somewhat rarely find a small, circular or 

 oval avicularium, almost entirely immensed but with the point somewhat project- 

 ing; its broadly rounded mandible is as a rule directed obliquely outwards and 

 proximally, more rarely quite proximally. 



Of this species I have examined some few colonies which occur in the form 

 of one-layered, hollow expansions. 



Formosa Channel, Lat. 23" 20' N., Long. 118" 30' E., 17 fathoms depth (Andrea). 



