ALOYONAKIA ".r. A. THOMSON ANII DOKls i. MACKINNON. ll'il 



of the stem is missing. The stem has a maximum diajiielei of -1 

 mm. ; the average diHiueter of llie larger brandies is 2 mm , and 

 of the twigs, 1 mm. Anotlicr specimen, al>o imomjilete, lias a 

 height of 16 cm., witli a span of 11 cm. The ioweupart of llio 

 stem is overgrown Ijy a sponge. 



Polyps occur here and there on the branches, but tiiey are 

 mainly coiihned to the twigs, along each siile of which they are 

 arranged alternately in a single row. Frequently this arrange- 

 ment becomes irregular, the polyps encroach on the middle line, 

 or a double row may he formed along each side. Tlier<- arc 

 ahoul fifteen polyps to 1 cm. in each row. 



The polyps are small, -S-'To mm. in height, chibslia|)t'd, trun- 

 cate, and turned upwards towards the tip of the twig. They 

 are covered with closely-fii ting, elongated spicules arranged 

 transversely, which cither interlock by means of their dentate 

 margins, or overlap one another ; the abaxial rows are composed 

 of about sixteen such spicukis arranged in an imbricate manner. 

 Similar spicules form a low, eight-rayed operculum. The Sjiicules 

 of tlie ctenencliyma are like those of the polyps, but follow the 

 loTigituiliiial diiection of the stalk and form a sort of pavement 

 over its suiface, adjacent spicules being clcselj' interlocked by 

 their teeth. The calcareous internodes of the axis bear fine 

 longitudinal ridges, which are dentate at the upper and lower 

 ends of the joint. The spicules are small, colourless, somewhat 

 flattened spindles and lancet-shaped plates, fieqnently curved, 

 and hearing numerous sharp, tooth-like warts, which are usually 

 more strongly di'velopedon oneside of tliespicule than the other. 

 The following measurements wei'e taken of length and breadth 

 in millimetres:— -238 x 085; -17 x 008; ■]o6 x 051. 



There are also numerous smaller spindles anil forms approach- 

 ing clubs:— 153 X V2r, ■ ll-J x 035 ; -085 x 031 ; -008 x 017 

 mm. 



The colour of the colonies is pale-brown to cream-white, the 

 axis occasionally tinged with pink. 



Locality. — Eleven miles east of IJroken Hay. 



Genus A C A N T II I ) I S I S, Wriyhl and Slttder. 



ACANTHOISIS FLAHELLUM, Wriyht and Sltider. 



(Plate Ixii., Hgs. 1 and 2.) 



Acanthoisis flabelluin, Wright and .Studer, Chall. Ue|)., Zool., xxxi., 

 1889, pp. 45 46, pi. viii., figs. 1, la., lb., pi. ix., fig. 12. 



Stations 22, 47 and 53. 



Some very fine fan shaped specimens of an orange-brown 

 colour agree with Wright and Studer's description of Acanthoiais 



