250 SIDNEY F. HAHMER. 



shorter than in the type, and barely project beyond a slight 

 web-like lamella which connects them along the distal part of 

 the main sclerite. In f, possibly from N. Australia, the b 

 operculum (fig. 17) is short and broad,^ its main sclerite 

 otherwise resembling that of the type, but it has only four 

 teeth, which are stout and erect. The teeth of a are vesti- 

 gial, and their web-like connection is just indicated. 



A mounted fragment of specimen (&) shows a curious 

 abnormality. One of the zooecia is unusually large, and has 

 a twin operculum, formed of two halves, each of full size, 

 with its own convex border ; but the two are united laterally, 

 their main sclerites being here continuous as well as the rest 

 of the opercula. The zocecium has a partial calcareous 

 septum dividing the proximal part only of the cryptocyst 

 into two halves. This septum is in the line of union of the 

 two halves of the operculum, as is also the single median 

 process of the zocBcium. The growing edge of the colony 

 had at this point met another lobe of the same colony. The 

 interference thus produced probably resulted in the imperfect 

 longitudinal division of this part of the growing edge. The 

 double zocecium is separated from the point of union of the 

 two lobes by two imperfect zooecia, without orifices or median 

 processes. 



The diameter of the b opercula is about 460 fx ; that of the 

 A opercula averages about 470 ju, the extreme measurements 

 taken being 350 fx (/) and 540 fx (b), both these extremes 

 departing considerably from the mean of their own specimen. 



3. S. tubulosa, n. sp. Figs. 3, 22, 23. 



S. magnilabris, Hincks,^ 'Ann. Nat. Hist.' (5), viii, 1881, 

 p. 7; and (5) ix, 1882, p. 123 ("Bass's Straits"). 



Cryptocyst joining the basal wall, angulated and often 



' Considerable variations oecnr in other species in the relative breadth of 

 the opercula. 



' It may be presumed that Mr. Hincks's remarks refer to the specimen 

 here described. 



