468 MR. A. W. WATERS ON 



spines, the next zocecium has seven spines., while the younger 

 zooecia liave usually three spines, two outer ones and one inner, 

 though there may be occasionally two or four spines instead of 

 three. The area is less than half the length of a zooeciuni, and 

 the pedunculate avicularia are placed at about half the height 

 of the area, whereas in B. ciliata they are much below it. The 

 avicularia ai^e of moderate size and similar in shape to those of 

 B. ciliata ; however, avicularia do not occur on any of the lower 

 zooecia, so that, counting from the primary, no avicularia will be 

 found before about the 18th zoa3cium. 



The pedunculate ovicell, directed laterally as in B. ciliata, is 

 situated on the inner side near the distal end. 



Loc. Taken in tow-net, Chuaka Bay, Zanzibar (515); Wasin, 

 Brit. E. Africa, 10 fath. (500), on Steganoporella magnilahris; 

 Chuaka, 2-3 fath. (512), collected by Crossland. 



Stirparia exilis MacGillivray. (PI. LXYI. figs. 1-3.) 



Stirparia exilis MacG. " Desc. of New or Little-known Polyzoa," 

 pt. xiii. Proc. Roy. Soc. Yict. n.s. vol. ii. p. 107, pi. iv. figs. 1-1 b 

 (1890). 



In the Wasin specimens the lower part of the stem is buried 

 in sponge and cannot be completely examined ; the upper part is 

 annulated for a short space ; the rest is smooth, unjointed, and 

 without any strengthening rods, but at irregular intervals there 

 are contractions, or sometimes two or three together, with rosette- 

 plates across the stem in places. Although these stems differ 

 from those of the other two species found, yet they are divided 

 up by these contractions into lengths often about equal to those 

 of S. dendrograpta ; however, the growth is much simpler, so 

 that, perhaps, /S'. exilis may ultimately have to be placed in 

 another genus. Fresh branches are given off at right angles 

 to the main stem and start from an expanded disk (fig. 3). 



The tuft is 5-6 mm. long, and the zocecia face to the outside 

 of the tuft. There are about 12 tentacles. The area is about 

 two-thirds of the length of a zooecium ; there are three spines, 

 or, in parts two; and oidy a very few, almost globular, avicularia 

 have been seen (about two in each tuft), and these are short with 

 apparently a wide mandible rounded at the end. The avicularia 

 are attached just below the area and there are no ovicells, only 

 the commencement of one. MacGillivray found neither avicularia 

 nor ovicells. 



The opercular opening is low down. At a bifurcation one 

 zocecium extends up a short distance on the opposite side of the 

 bifurcation (fig. 1), and this is well shown in the British Museum 

 specimens of S. exilis MacG., from Port Phillip Heads. 



The mounted specimen from the ' Challenger,' named S. glabra, 

 is S. annulata Mapl., though there are mounts of a stem of a 

 species which are like those of S. glabra and S. dendrograpta. 

 Busk's figure, however, seems to show S. glabra H., so that we 

 have a puzzle ; but we may be right in concluding that S. glabra 



