REPORT ON THE CALCAREA. 45 



frequently slightly curved, usually inwards, twice as thick as basal ray; length inconstant, 

 varying from 0'025 mm. to 0"12 mm. 



Colour. — White. 



Habitat— Station 163, April 4, 1874 ; lat. 36° 56' S., long. 150° 30' E. ; depth, 120 

 fathoms ; off Twofold Bay, Australia. 



Heteropegma, n. gen. 



Syconidse with articulated tubar skeleton, the supporting skeleton of whose strongly 

 developed cortex consists of triradiate and quadriradiate spicules, quite different in size 

 from those of the parenchyma. 



Heteropegma nodus gordii, n. sp. (PI. I. fig. 7 ; PI. IV. figs. la-Id). 



This species, represented in the Challenger collection by two specimens, forms colonies 

 of a rather Asconoid appearance. The tubes, sometimes standing vertically, sometimes 

 lying horizontally, ramify and interlace, thus constituting a kind of knot in which neither 

 beginning nor end can be discerned. The individuality of the tubes is expressed only by 

 oscula, these latter being naked. In one specimen, from Australia, the oscula are numer- 

 ous, while, if present at all, they seem to be much more scanty in the other, from 

 Bermudas. It must be said, however, that this latter specimen was quite crushed and 

 crumpled. 



The size of the oscula is inconstant, varying from 0'25 to 1 mm. in diameter. Both 

 the surfaces are rough. The average thickness of the walls is 1 mm., the diameter of the 

 inner cavity 1 mm. in the Australian specimen, 2 mm. in that from Bermudas. The radial 

 tubes are of irregular outline, and show a great tendency to ramify (PL IV. fig. la). 



The specimen from Bermudas proved to be sterile ; but in the radial tubes of that 

 from Australia I found some Amphiblastulse. 



Skeleton. — The skeleton consists of minute tubar and gastric quadriradiate, of much 

 larger triradiate and quadriradiate cortical, and of triradiate oscular, spicules. 



Skeleton of tlie parenchyma. — The typical modifications of the tubar and gastric quadriradiates 

 are represented on PL IV. fig. la ; there are also amongst them triradiate spicules of the 

 same outlines and size, but they are not numerous. The tubar quadriradiate spicules are 

 regular, their rays either tapering from the base to a sharp point, or of cylindrical form 

 with truncated ends ; in both cases the proportion between the length and the thickness of 

 the rays at their base remaining the same (30 : 1), their length being O'OC mm., their 

 diameter - 002 mm. These regular spicules of the radial tubes are connected by all 

 possible intermediate stages with sagittal and irregular quadriradiate spicules supporting 



