BRYOZOA 81 



The opercula and mandibles are of the R. cellulosa type, being somewhat similar to 

 those of R. Couchii H., but perhaps the nearest relationship is with R. avicularis MacG., and 

 with the fossil variety R. rimata Waters, from which it differs in the shape of the avicularia. 

 R. magellensis Bush (collected by the Challenger off the Argentine, and also known from the 

 Falklands and Cape Horn) also differs in having small semicircular avicularia on the anterior 

 and dorsal surface, whereas in R. antarctica they are elliptical, further in R. magellensis the 

 labial semicircular avicularia are constant, and the two species can be distinguished by means 

 of the ovicells. Btjsk's description of R. magellensis in the « Challenger Report » requires 

 correction, as in the Challenger spécimens there are distinct vibices and also numerous 

 semicircular avicularia on the dorsal surface. Unfortunately Busk does not seem to hâve 

 incinerated, or boiled in caustic any of the Reteporœ, and thus sometimes overlooked vibices 

 and small avicularia. 



Habitat. — Exp. Antarct. Belge. 



N° 3og, Tangles II. Lat. 71° 14' S.- Long. 89° 14' YV.; 460 met.; +o.3 C. 

 N os 345, 1047, Tangles IV. Lat. 71° 18' S.- Long. 88° 02' W.; 435 met.; — o.3 C. 

 X" s 60S, 620, 621, 683, 991, Tangles VIII. Lat. 70 00' S.- Long. 80" 48' W. ; 58o met.; 

 -fo.g C. 



Retepora protecta sp. nov. 



(PI. VI, figs. la-e) 



The zoarium is cup-shaped, with rather small fenestrse about i.o mm -i.4 mm long, and 

 about o.8 mm wide. There is one nearly flat pièce from 620, about 35 mm X 20 mm . 



The zoœcia are rhomboidal, separated by narrow lines, and but slightly convex ; surface 

 iaintly pitted with the edges of thèse shallow pits straight, thus forming a kind of net work. 

 The peristome in front is irregularly notched, and often is raised as a plate, which may even 

 turn forwards at right angles to the axis of the zoarium. There is a fissure or pore at the side 

 of this plate, but it is only formed by the junction of the opposite walls of the peristome, 

 and this will be the labial fissure or pore, which in most species, where it occurs, is médian. 

 The distal portion of the peristome also sometimes extends beyond the aperture. In young 

 zoœcia there are 6 spines, but in the older ones there may be one délicate spine on each side, 

 though as a rule spines are absent. On the front of the zoœcium there is usually one small 

 elliptical avicularium. The dorsal surface has irregular vibices, and round the edge of the 

 fenestrœ there are numerous small avicularia. The ovicell is not raised, and frequently it is 

 not readily distinguished, there is a straight mark on the front, but this does not seem to be 

 a fissure. There are 12 tentacles, and also suboral glands, and in the spécimens N° 242 there 

 are ova and testes with abundant spermatozoa. 



Except in a baclly preserved dry spécimen, from N° 683 the shape of the zoarium 

 cannot be recognised, in this however it arises from a broad base, and is cup-shaped. The 

 meshes are smaller in this spécimen, than in the others, but the identity is established, although 

 it is badly preserved. There is also a small stout spécimen from N° 3og (PI. VI, fig. 9) which 

 shows neither reticulation nor anastomoses and which I at first labelled R. porcellana MacG. 

 It is not in good condition for détail examination, but the opercula and other zoœcial characters 

 correspond with those of the reticulate R. protecta ; and at présent we may consider it R. protecta 

 var. crassa. 



XI 



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