1900.] MARINE FAUNA OF CHRISTMAS ISLAND. 129 



Olathrina primordialis (Haeckel). 



1872. Ascetta primordialis var. protogenes Haeckel (8. ii. p. 16, 

 Atlas, pi. ii. fig. 13). 



1892. Olathrina primordialis Lendenfeld (8. p. 195). 



The specimen consists of a small mass about 10 mm. in area by 

 5 mm. in height. No oscules are visible, but this is probably due 

 to the contracted state of the sponge. 



The spicules, which are equiangular and equiradiate, are very 

 small and slender, being smaller than in the typical Mediterranean 

 form, and much smaller than in the Australian form named 

 Olathrina primordialis var. protogenes by Carter (3. p. 510) and 

 C. protogenes by Dendy (5. p. 58). The rays, which are 70 ju by 

 6^, taper gradually to a rather sharp point. 



Leucandra sp. 



The specimen forms a small oval mass 3x2 mm. plugging up an 

 oscule of Tetilla ternatensis. The outer surface bristles with the 

 projecting ends of stout oxeotes which pass through the dense 

 mass of tri-radiates ; gastral quadri-radiates can here and there 

 be made out in spaces in the interior. 



Spicules. Oxeotes 1500 x 70^u ; tri-radiates, rays sharp-pointed, 

 often wavy, 245 x8ju; quadri-radiates, tangential rays curved 

 inwards towards the apical ray ; tangential ray 105 x 18 fj, apical 

 ray 35 p in length. 



Canal-system : pores lead into incurrent spaces surrounding 

 groups of large oval ciliated chambers 85 p in diameter, and groups 

 of the latter open into excurrent spaces. 



The species is probably new ; but since the specimen is very 

 small and has been damaged in extraction, owing to its being 

 partly involved in the tissues of the Tetilla, no specific name has 

 been given. 



Chondeosia reniformis Nardo. 



One typical specimen occurs ; it is bluish black on the upper 

 surface ; pale brown below, where it is attached by a narrow 

 ridge to the rock. The one rather large oscule has a membranous 

 slightly serrated margin. The colour on sectiou is dirty white. 

 I have exnmined some fragments of the type specimen of Chon- 

 droma ramsayi Lendenfeld, and agree with Topsent in regarding 

 this species as a synonym of O. reniformis. 



A noticeable feature in the Australian specimen is theabundance 

 of pigment in the interior, giving the sponge a slaty colour on 

 section. 



Distribution. Mediterranean ; Kattegat ; Tadjurra, Gulf of 

 Aden; Port Jackson ; Amboina ; Christmas Island; Galapagos 

 Islands. 



Chondrosia plebeja O. Schmidt. 

 1868. Chondrosia plebeja O. Schmidt (14. p. 1). 

 There are eight specimens, seven in alcohol and one in formol ; 

 Proc. Zool. Soc— 1900, No. IX. 9 



