SynojJsi.i of the Australian Calcarea. Heterocada. Ill 



dermal surface. Beneath the dermal surface, but apparent 

 only on the upper surface of the sponoe, is a distinct lawyer 

 of subdermal sagittal triradiates with inwardly-directed 

 basal ray. The dermal skeleton is made up principally oi" 

 subi-eguiar triradiates of various sizes, placed horizontally, 

 but with no definite ariangement ; amongst these very 

 minute, slender oxea are scattered, rare on the upper surface 

 of the sponge but abundant on the lower ; around the 

 osculuin these oxea are numerous and a few are much lai-ger 

 than the rest. Around the main exhalant canals there is a 

 layer of small sagittal triradiates. The forms and dimen- 

 sions of the different spicules are as follows: — (1) Triradiates 

 of the exhalant canals ; sagittal, rays conical, fairly sharply- 

 pointed ; basal straight, orals usually slightly incurved or 

 recurved ; basal commonl}^ somewhat shorter than orals, 

 which measui-e about ()i6 b}' 0012 mm. Just below the 

 osculum I have seen short apical rays in a few of the sagittal 

 radiates. (2) Triradiates of the main skeleton ; subregular 

 or slightly sagittal ; rays usually straight, conical, gradually 

 sharp-pointed, rathei- slender, up to about 0"3G by 0-024 mm. 

 (3) Subdermal sagittal triradiates ; similar to the foregoing 

 but a good deal smaller, and with the basal ray much longei- 

 than the others. (4) Dermal triiadiates ; subregular, with 

 long, conical, gradually sharp-pointed rays varying greatly in 

 size, up to about 0-54- by 0-045 mm. (5) Oxea; mostly very- 

 minute and slende]-, sharjdy-pointed at each end, with one 

 end rather thicker than the other ; straight ; often slightly^ 

 rougliened ; usually short, but varying greatl}^ in length ; 

 around the osculum a few much stouter ones occur, Init still 

 very small. 



Localhy. — Near Port Phillip Heads (Sorrento Reef, coll. 

 J. B. Wilson). 



67. Vosmaeropsis ivilsoni, n. sp. 



Sponge colonial, consisting of short, thick, sub-cylindrical 

 or truncatedly conical individuals united together by their 

 bases into smaller or larger agglomerations, which may 

 attain a diameter of nearly five inches. Each fully grown 

 individual has a circular. osculum at its summit, which may 

 or may not have an oscular fringe, adjacent individuals of 

 the .same colony sometimes differing in this respect. The 

 osculum is often provided with a very distinct, membranous 

 diaphragm, situated a short distance within its margin. Tlie 



