REPORT ON THE TETRACTINELLIDA. 
103 
II. Microsclere. 2. Microxea, rod-like, covered with numerous small spines, 0’0127 
mm. in length. 
Habitat . — Gulf of Manaar. 
Genus 7. Nethea,^ n. gen. 
Theneidse, resembling Poecillastra in the characters of the spicules, but distinguished 
by peculiar dichotrisenes, with scarcely developed rhabdomes. 
Nethea nana (Carter). 
Tisiplionia nana, Carter, Ann. and Mag. Nat. Hist., ser. 5, vol. vi. p. 138, pi. vii. fig. 43, 1880. 
Sjponge. — Lamelliform, thin, incrusting or burrowing ; surface even. 
Spicules. — I. Megascleres. 1. Oxea, fusiform, curved, 0‘38 by 0'014 mm. 2. 
Dichotrisene, rhabdome reduced, represented only by a short, conical, blunt process, 
0‘085 by 0'042 mm. ; chord of cladome 0‘7 mm. 
II. Microscleres. 3. Microxea, fusiform centrotylote, 0'056 mm. long. 4. 
f Spiraster (a stellate, with a tendency to assume a spinispirulate form. Carter), 0*0125 
mm. long. 
Colour. — White . 
Habitat . — Gulf of Manaar. 
Genus 8. Placinastrella, F. E. Schulze. 
The megascleres are calthrops, triods and oxeas ; the calthrops when occurring near 
the surface is orientated like a trisene, which it then much resembles. The microscleres 
are of two orders of size, a larger consisting of tri- and di-actinose asters, and a smaller, 
chiefly confined to the ectosome, and consisting of tetra-, tri- and di-actinose asters. 
Placinastrella copiosa, F. E. Schulze. 
PlaMnastrella copiosa, F. E. Schulze, Zeitschr. f. wiss. Zool., Bd. xxxv. pp. 434, 449, 1880. 
Sponge. — Small, a segment of a sphere seated on a flat base, bearing near the summit 
a single oscular tube. Ectosome excavated by subdermal cavities, and traversed by 
numerous minute asters and microxeas, the latter near the surface being directed at right 
angles to it, and thus minutely hispidating it. 
Spicules. — I. Megascleres. 1. Calthrops with four equal actines in the choanosome, 
near the surface, trisene-like, the longest actine 0T42 mm. long. 2. This passes into 
triods and oxeas. 
1 The name Nethea is an anagram of Thenea, itself a fortuitous combination of letters. 
