1900.] MARINE FAUXA OF CHRISTMAS ISLAND. 137 



swellings along the body, one of the ends attenuated sometimes to 

 a blunt point. Amphidiscs 18 /z. 



The characteristic feature of the new variety lies in the 

 strongyles with their peculiar swellings ; these may, however, be 

 dependent on some pathological cause such as the presence of a 

 parasite, but I was unable to find any such organism. [In several 

 descriptions of this species the dermal diactines are described as 

 tylotes. In the type specimen from Port Darwin the ends of the 

 strangles are very slightly enlarged, a feature slightly ex- 

 aggerated by the artist in the figures (11. p. 435, pi. xlii. fig./) ; 

 but there is no trace of terminal enlargement in the spicules of 

 specimens from the Mascarenes, Madras, and Christmas Island.] 



Desmacella sp. 



A few small broken-up pieces of a very soft dark reddish-brown 

 incrusting sponge, with a few crater-like oscules. The skeleton 

 forms a unispicular network, the meshes of which are triangular 

 and quadrangular and made up of styles, oxea, and strongyles. A 

 few long slender toxa and one or two sigmata, together with some 

 slender raphides, are present. The skeleton is renieroid, and 

 spongin entirely absent. The dimensions of the spicules are : — 



Styles (not rare) slightly curved, 150 x9ju; strongyles (rare) 

 straight, 126 x6fi. Oxea (very abundant), curved, 180 x 7 p. 



Microscleres — toxa 48 x *5 li (rare) ; sigmata 24 fx (very rare) ; 

 raphides (rare), 108 x 1*5 li. 



This species, which appears to be new, has not been named 

 owing to the uncertainty as to whether all the above-mentioned 

 microscleres seen in the preparations really belong to the sponge ; 

 several kinds of obviously foreign spicules were included. 



Stylotella irregularis, sp. n. (Plate XII. fig. 4; Plate 

 XIII. figs, b' a-d.) 



Sponge incrusting or forming free irregular lamellae ; colour 

 pale brown ; with several small circular oscules 2 to 3 mm. in 

 diameter on the upper surface. 



Skeleton forming a rectangular network, the meshes being for 

 the most part unispiculate, but with a few slender primary lines of 

 spiculo-fibre 2-4 spicules thick. 



Spicules. Styles 186 x9^, smooth, straight or slightly curved. 



Oxea 204 x 9 li, curved. 



Strongyla 150 x 10 li, straight or slightly curved. 



Slender oxea 150 x 4ll, occasionally with a central fusiform 

 enlargement, rare and scattered in the tissues. 



This species is very near Petrosia contir/nata Thiele, from 

 ebes (Zoologica, Stuttgart, 1899, Heft 24, ii. p. 20), but differs 

 mainly in possessing slender fusiform oxea ; unfortunately the 

 central swelling is not shown in PI. XIII. fig. 6 d. 



Stylotella sp. 



Specimen incrusting, 2x1 c.c. in area, and *25 to *5 c.c. in thick- 

 ness ; pale brown, very soft, with several oscules 1 mm. in diameter. 



