98 U.S. NATIONAL MUSEUM BULLETIN 2 72 



conspicuous; dermal membrane well developed, often separated from 

 the underlying symplasm. Skeleton consisting of rather thick vertical 

 spicule fibers, coated together by a fair amount of spongin, and of a 

 somewhat slimmer arrangement of transverse and radiating spicule 

 fibers. Consistency of live sponge moderately hard, firm but brittle. 



Megascleres stout, often cylmdrical, but usually typically fusiform 

 amphioxea, entirely smooth or rarely inconspicuously microspined; 

 length range 195-330 m> width range 13-18 m- 



Microscleres absent. 



Gemmoscleres birotulates with a very slender finely granulated 

 shaft, and terminally with flat rotules of slightly unequal diameter; 

 faces of rotules distinctly granulated, arrangement of granules almost 

 radial; margin of rotules irregidarly crenulated, rarely bearing dis- 

 cernible teeth; length dift'erences of birotiUates moderate: length 

 range of larger series 38-52 n, of smaller 34-45 n; width range of low^er 

 rotiUe 24-28 fx, of upper 20-23 n; thickness of shaft 3-4 ijl. 



Gemmules spherical and large, scattered through skeletal mesh- 

 work, more abundant m basal parts, diameter ranguig 510-600 n; 

 pneumatic layer veiy thick and irregular, in places much higher than 

 the longest gemmoscleres, consisting of minute air spaces; gemmo- 

 scleres embedded in this coat strictly radially, with their larger rotules 

 firmly inserted in the inner gemmular membrane; outer parts of 

 pneimiatic layer devoid of gemmoscleres, but strongly reinforced by 

 a varying number of normal megascleres; outer gemmular membrane 

 distinctly corrugated, and of pale yellow color; foramen simple or 

 bearing a shallow peripheral collar. 



Distribution. — Apparently restricted to an area reachmg from 

 Central Australia east to the Dividing Range and north to Queens- 

 land, preferring inland waters of slight salinities. 



Color in life. — Light tan to brown. 



Discussion. — This species represents one extreme in the inter- 

 grading series of gemmosclere characters, and the length differences 

 between the longer and shorter sets of its birotulates are not greatly 

 pronounced. Other unusual criteria, as the participation of normal 

 megascleres in the outer protection of the gemmules and the small 

 size differences between the upper and lower rotule, makes H. cape- 

 welli, the type species of this genus, a rather atypical member of 

 Heterorotula. Extensive studies in Australian waters (Racek, MS.) 

 revealed that even its optimal habitat is quite unusual, since it seems 

 to be restricted to slightly brackish waters of the arid parts of Aus- 

 tralia. The intrageneric relationship will be dealt with in detail in 

 a forthcoming paper by the writer. 



