COLLECTED BY THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 447 



about O'l mm. to 0*6 mm., with a maximum diameter of about 0'002 mm. The 

 smaller toxa have a well-marked bend in the centre of the spicule, with, as a rule, 

 straight arms. In the longer toxa the bend is sometimes well defined, but is 

 often slight, or inappreciable. 



Clathria rhaphidotoxa somewhat resembles Clathria meandrina Ridley (14) in 

 external appearance, the surface of both being raised up into similar meandrine 

 ridges, but it differs from that species in the arrangement of the skeleton and in 

 the size and shape of the spicules. On the other hand, the spicules of Clathria 

 rhaphidotoxa and Rhaphidophlus filifer Ridley and Dendy (15) are somewhat 

 similar, although differing in various details, but the two species are clearly 

 marked off from each other by the different arrangement of the dermal skeleton 

 as well as by their external appearance. 



Sub-family myxillin^. 

 Myxilla simplex (Baer). (Plate XXXIX, figs. 1 b and 4 c.) 



Station 478. Table Bay, shore. May 1904. 



Station 482. Reit's Bay, Saldanha Bay, shore. 21st May 1904. Seven 

 specimens. 



Station 483. Entrance to Saldanha Bay, 25 fathoms. 21st May 1904. Sixteen 

 specimens. 



This species, which was described from one small specimen taken off Cape Town 

 (l), appears to be common off the west coast of Cape Colony. The numerous speci- 

 mens in the collection agree very well with the description of the type. They are 

 all more or less rounded or oval in shape. The surface is grooved and the oscula 

 are, as a rule, numerous, the largest measuring about 6 mm. in diameter. The 

 sponges are rather firm to the touch but easily broken, and they are only slightly 

 compressible. In external appearance they closely resemble spirit specimens of 

 Myxilla incrustans (Johnston). Many of the specimens apparently grew quite free 

 of any support. Others are encrusting the bases of dense hydroid colonies, while 

 the Table Bay specimens are growing among the roots of a large sea- weed in company 

 with Esperiopsis informis n. sp. 



The smallest specimen is a little encrusting patch, 7 mm. in diameter, growing 

 at the base of a young Homceodictya compressa (Esper). The remaining specimens 

 vary in size from 45 mm. by 30 mm. in diameter, with a height of 20 mm. to 

 125 mm. by 72 mm., with a height of 53 mm. 



The spicules vary in size to some extent in the different specimens, but in the 

 majority the measurements agree very well with those given for the type. 



The measurements are as follows : — -(l) Styli, 0"16-0'22 mm. in length, with a 



maximum diameter of 0'012 mm. (2) Tornota, 0*16-0*2 mm. by 0*008 mm. 



(3) Anchorse spatuliferse, maximum length about 0*024 mm. (4) Sigmata, from 

 TRANS. ROY. SOC. EDIN., VOL. L, PART II (NO. 15). 63 



