12 



The dermal pinules are sleuder and very variable in length. In the specimen 

 from the Laccadives they are on an avei'age 300-400 z^, in the one from the 

 Andamans 500-600 /^ long. The upper, spined part of their distal radial ray 

 is broader in the former than in the latter. The basal smooth part of the radial 

 ray is 40-50 M long and 7 ," thick (pi. Ill, f. 9, pi. IV, f. 14). The four basal 

 rays are sharp-pointed, pretty stout, and 40-50 ^ long ; their terminal parts are 

 covered with tubercles or small spines. The pinules of the oscular sieve-plate 

 are a little shorter, but otherwise similar to the dermal ones. Those of the walls 

 of the excurrent canals are very much shorter and considerably more slender. 



The dermal macramphidiscs have hemispherical terminal discs with 6-8 

 broad and spade-Hke marginal teeth. The shaft bears rounded tubercles which 

 form a ring round its centre and are sparsely and irregularly scattered over the 

 other parts (pi. Ill, f. 3, pi. IV, f. 3, 4). The macramphidiscs of the Laccadive 

 specimen are considerably larger than those of the Andaman specimen. In the 

 former they are 300 /^ long and have terminal discs 100 M broad, in the latter 

 they are mostly only half as long and have terminal discs only 60-70 h broad 

 (pi. Ill, f. 3, pi. IV, f. 3, 4). 



Mesamphidiscs are very numerous in the walls of the excurrent canals of 

 the Andaman specimen. They vary considerably in size, being 50-130 /* long, and 

 are clearly distinguished from the stout macramphidiscs described above by the 

 greater height and more slender form of their strongly curved terminal discs,, 

 which usually have 8 narrow marginal teeth (pi. Ill, f. 4, 5, pi. IV, f. 5). Not 

 unfrequently the marginal teeth of the two opposite discs are so long as to come 

 in contact with each other. Then the whole spicule attains an ellipsoidal shape. 

 The shaft bears blunt, irregularly distributed spines, which are higher in its 

 central part than towards its ends (pi. Ill, f. 4, 5, pi. IV, f. 5). 



Micramphidiscs 30-50 ^ long are abundant in the dermal membrane and 

 in the oscular sieve-plate, chiefly in the former. Their terminal discs are hemi- 

 spherical and have 10-12 narrow marginal teeth. The shaft is slender, thicker 

 in the middle than towards the ends. 



Micro-oxyhexactines are abundant in the parenchyme. Their rays are 

 50-60 H- long, at the base about 3 H- thick, straight and covered throughout with 

 small tubercles so that their surface appears rough. Occasionally similar spicules 

 with only 5 or 4 rays, pentactines or tetractines, are met with (pi. Ill, f. 11-13, 

 pi. IV, f. 10-12). 



On account of the differences in the shape and size of their dermal pinules 

 and in the dimensions and abundance of the macramphidiscs, the two specimens 

 should, I think, be considered as representing two distinct siibspecies or local 

 varieties. I accordingly distinguish them as Hyalonema indicum laccadivense 

 and Hyalonfma indicum andamanense. 



