480 MR. A. W. WATERS ON 



Zool. Results, pt. iv. p. 441, pi. xlii. fig. 1 (1899) ; Thornely, 

 " Mar. Polyzoa of the Indian Ocean," Trans. Linn. Soc, Zool. 

 vol. XV. p. 141 (1912). 



Caberea retiformis Smitt, "Floriclan Broyzoa," pt. i. p. 16, pi. v. 

 figs. 43-46 (1872); Thornely, "Ceylon Pearl-Oyster Fisheries," 

 vol. iv. Suppl. Rep. xxvi. p. 109 (1905). 



? Cauda fossilis Waters, Q. Journ. Geol. Soc. vol. xxxvii. p. 322, 

 pi. xvi. figs. 51, 52 (1881); MacG. " Tert. Polyzoa of Victoria," 

 p. 25, pi. iii. figs. 12-14, Trans. R. Soc. Vict. vol. iv. (1895). 



The specimens from Zanzibar have the scutum very narrow, 

 pointed distally, and rounded proximally, as described by Miss 

 Philipps, and I follow her in considering them to be the form 

 described by Smitt, and although allied to C. arachnoides they 

 seem quite distinct. It occurs in the Atlantic, the Indian Ocean, 

 and the Loyalty Islands, without any connecting links being 

 known. Caberea crassimarginata B., of the ' Challenger,' and 

 Scriqjocellaria clypeata Haswell, seem to belong to this group. 



No anterior avicularium has been described, but sometimes 

 there is one attached to the inner side of the zocecium, and then 

 it is usually just below a bifui-cation. The avicularian chamber 

 is wide, and the mandible is triangular. There are two vibracula 

 at a bifurcation.' 



Both Smitt and Levinsen have considered this species as having 

 no articulation, and as the chitinous tube is often entirely covered 

 by the calcareous wall in which there is as yet no rupture, it 

 requii^es decalcification to study the articulation, which is peculiar 

 and seems to difler from that of any other species examined. 

 In the younger branches there is no sign of articulation, but in 

 the older ones there is one chitinous tube on the inside of one of 

 the tioo branches, but not of both, and a point to be noticed is 

 that when the chitinous tube is on one side, say to the right, it 

 is in the next branch on the left, in the one following on the 

 right, and so on alternately, though in a few cases in the older 

 parts of the colony I have seen a chitinous tube to each branch. 

 In C. arachnoides Lamx., as I have shown*, there are two 

 chitinous tubes, one on the inside of each branch. The articula- 

 tion of C. tenuis MacG. is somewhat similar. 



When decalcih'ed, a chitinous tube is shown in the peduncle of 

 the scutum, just as is seen in the base of many spines. 



Near the base of the vibracular seta there is a projecting 

 delicate free arch at right angles to the axis of the seta, and in 

 other species of the Scrupocellaridao there seems to be a similar 

 structure, though not so pronounced. 



One of the cross radicle tubes usually connects the two new 

 branches at a very short distance from the bifurcation, and this 

 may partly account for rupture at the articulation so seldom 

 taking place (see fig. 1). 



* Ann. Mag. Nat. Hist. ser. 5, vol. xx. p. 89, pi. iv. fig. 7. 



