430 "prof. J. a. THOMSON AND MR. W. D. HENDERSON ON [Apr. 10, 



The spicules of the general crenenchyma, are all of one type — 

 spindles covered with rough warts, which are arranged in regular 

 whoi-ls, and often hlunt at both ends. Some of the spicules are 

 yellowish-amber colour, often almost colourless at the tips ; others 

 are quite colourless. Then- measurements, length by breadth in 

 millims., are as follows : — 



Coloured: 0-2 X 0-05; 0-12 x 0-06; 0- 16x0-05; 0-16 x 0-04; 

 0-14 X 0-05. 



Colourless : 0-06 x 0-03 ; 0-08 x 0-04 ; 0-12 x O'OS ; 0-14 x 0-05 ; 

 0-1 X 0-04. 



Locality. Wasin Channel, 10 fathoms. 



(B.) — Another colony forms a thin encrustation on a piece of 

 bivah'e shell, about 25 mm. by 30 mm., with nine stems rising at 

 various angles. Three of the stems lie on the under concave 

 surface of the shell and keep close to it ; the four longest on the 

 other side extend to 65-80 mm. from the shell. Two have a 

 single branch. The gi'eatest breadth is about 2 mm. Tliere is 

 a slight flattening in the plane in which the polyps for the most 

 part ai'ise. The general colour is a cpiiet orange. The verrucae 

 are inconspicuous and for the most part lateial ; some of them 

 show eight distinct marginal lobes. The polyps are pure white. 

 A longitudinal groove is distinct for a short distance from the 

 base. The spicules are spindles with warts in whorls 0*12x0"04, 

 0-14 X 0-04 mm.; and doid^le spindles 0-13 x 0-06, 0-12 x 0-05; 

 and a few small almost oibicular forms. 



This form appi'oaches ;S'. kollikeri Wi'ight & 8tuder, but (lifters 

 from it in the size and jirominence of the veri'uca? and in the size 

 of the spicides, but it is connected to that species by Suberogorrjia 

 kollikeri^ var. ceylonensis. But the Zanzibai' form has smaller 

 verrucfP and spicides than the Ceylonese variety, and the series 

 may be regarded as illustrating progi'essive variation. 



Locality. Kokotoni Hai-bour, Zanzibar West, 5 fathoms. 



Family Melitodid^. 



Wrightblla erythr.ea Gray = Mopsea erythr^a Klunzinger. 

 (Plate XXVllI. fig. 10.) 



Small, irregularly blanched, rose-ied colonies, fixed to coral. 

 The branches ai"e not always confined to one plane. Tlie following 

 measurements wei-e taken of height and breadth in millims. : — 

 15x23; 23x8; 15x8. The specimens agree well with Klun- 

 zinger's description of Mopsea erythrcea, e. (j. in the pi-esence of a 

 single i"ed spicule at the base of each tentacle and in the dimensions 

 of the spicules generally. 



Localities. Wasin, low tide, growing on coral ; Prison Island, 

 Zanzibai' Hai-bour. Previously lecorded from the Red Sea. 



In the Aberdeen University Museum there is a specimen 

 fiom Samoa which is superficially identical with these. It is 

 labelled Mopsea eryihroia. 



