152 THE VOYAGE OF H.M.S. CHALLENGEE. 



form a quadrate lattice-work. They are usually curved slightly inwards. Opposite the 

 straight proximal radial ray which penetrates almost through the thickness of the body- 

 wall, a small distal protuberance is occasionally developed, though usually absent. These 

 pentacts, especially in the neighbourhood of the oscular margin, sometimes protrude 

 beyond the surface of the sponge, and form with their tangential rays, as in RosseUa, a 

 sort of veil over the slcin ; but this diflferentiation occurs only locally and exceptionally. 



The dermal membrane itself includes a large number of small, simple, roughened 

 oxytetracts, in which the arms, intersecting at right angles, seem to be usually some- 

 what bent inwards (PI. LVIII. figs. 2, 5). 



The gastral skeleton seems wholly destitute of hypogastralia, and consists merely of 

 tbe very numerous gastral oxyhexacts, in which pointed rays are thickly beset Avith fine 

 spines. The ray which projects radially inwards into the gastral cavity is usually cj^uite 

 as long as the five others (PI. LVIII. figs. 2, 6). The marginalia, which project in cufi"- 

 like form round the superior oscular margin, are smooth oxydiacts, 8 to 10 mm. in 

 length, without definite central swelling or formation of knots, and with simple pointed 

 ends. 



At Station 241 (lat. 35° 41' N., long. 157° 42' E.), from a depth of 2300 fathoms and 

 a red clay ground, the trawl brought up some flat fragments, 1 mm. in thickness, which 

 corresponded in their whole appearance to the above described Bathydorus. They 

 exhibited the same structure as the above, with the single exception of the parenchymal 

 oxyhexasters, in which the long terminal rays were never so thickly disposed in perianth 

 fashion, as was frequently the case in the above-described form. Here they all diverge 

 more or less, as was indeed occasionally the case above. The spinous gastral hexacts 

 exhibit somewhat longer radial rays than do those in the form already described. I do 

 not think, however, that these slight difi"erences justify the erection of a distinct species, 

 but believe rather that we have here to deal merely with a local variety, and therefore 

 refer these fragments without hesitation to Bathydorus Jimhriatus. 



2. Bathydorus stellatus, n. sp. (PI. LIX. figs. 1-5). 



In Messier Channel, ofi" Patagonia, right in front of Port Grappler (Station 307, 

 lat. 49° 24' 30" S., long. 74° 23' 30" W.), from a depth of 140 fathoms and a blue mud 

 ground, the trawl brought up a small inconspicuous sponge form, about 15 mm. in length. 

 The thin- walled saccular body was divided superiorly into two terminal tubes, 6 mm. 

 in breadth, with terminal apertures. On the otherwise smooth external surface, some 

 thin pointed spicules project obliquely outwards and upwards for 5 to 6 mm. At 

 the terminal oscular aperture no distinct crown of marginalia is to be seen, but this is 

 perhaps the result of slight injury. 



The parenchjTual spicules are long, narrow, straight or gently curved diacts, with or 



