EEPORT ON THE TETRACTINELLIDA. 
199 
This genus is evidently similar to Ecionema, but I retain it provisionally on 
account of the difference between the microxea wliich distinguishes it and the 
microstrongyle of the latter. The Ecionemid microstrongyle is probably derived 
from a minute aster, and does not exhibit an axial fibre, the Papyrula microxea is 
probably derived from a large aster, and does exhibit an axial fibre. If this distinction 
should hold good, the species Ecionema hacilUferum, var. ohtusum, Carter, would have 
to be included in Papyrula, since the microstrongyle which characterises it presents 
an evident axial fibre, and has been derived, not from the chiaster, but from the 
comparatively large anthaster. 
Papyrula helleri (0. Schmidt). 
Stelletta helleri, 0. Schmidt, Spong. Adriat. Meeres, SuppL, i. p. 32, pi. iii. fig. 8, 1864. 
Sponge. — Amorphous, surface smooth, cortex thin, cortical skeleton consisting of 
centrotylote microxeas. 
Spicules. — I. Megascleres. 1. Oxea, 1‘43 by 0'039 mm. 
2. DicTiotrisene, rhabdome proximally strongylate, 0'4 by 0'035 mm., protocladi 0‘06 
to 0‘09 mm. long, deuterocladi 0T.9 to 0‘24 mm. long. 
II. Microscleres. 3. Microxea, fusiform, centrotylote, 0’032 to 0T5 mm. by 
0'006 mm. 
4. Oxyaster, centrum small, confluent with the conical actines, a single actine 
0'02 mm. in length. 
Colour . — Black. 
Habitat. — Lissa, Adriatic ; depth, 35 fathoms. 
Papyrula candidata, 0. Schmidt. 
Papyrula candidata, Oscar Schmidt, Spong. Adriat. Meeres, SuppL, iii. p. 18, pL iv. fig. 1, 1868. 
Sponge growing in irregular rounded masses about 30 mm. in diameter. Cortex of 
the thinness of paper. 
Spicules . — I. Megascleres. 1. Oxea, slender, 0'816 mm. in length. 
2. Dichotrisene, rhabdome short, protocladus 0'071 mm. in length, deuterocladus 
0T775 mm. in length. 
II. Microscleres. 3. Microxea, centrotylote or not, from 0’05 to 0’25 mm. in 
length. 
Colour. — White externally, yellowish-green within. 
Habitat . — Coast of Algiers. 
The measurements of the spicules are based on mounted preparations presented by 
Schmidt to the British Museum, and are therefore unreliable. Schmidt gives the size of 
