DESCKIPTION OF GENERA AND SPECIES. 
Tribe TETRACTINELLIDA, Marshall. 
Demospongise with triaene or tetractine spicules or “ Lithistid ” desmas. 
Order I. CHORISTIDA, SoUas. 
Tetractinellida with triaene or tetractine spicules, but without “ Lithistid ” desmas. 
Suborder I. SIGMATOPHOEA. 
Choristida in which the characteristic microscleres are sigmaspires. 
Family I. Tetillid^, Sollas. 
Sigmatophora in which the characteristic megascleres are slender protriaenes. 
Tetilla, 0. Schmidt. 
The eetosome is never a cortex ; the mesoderm is a collenchyma ; and the chamber 
system eurypylous. 
Tetilla sandalina, Sollas (PI. I. figs. 16-27). 
Tetilla sandalina, Sollas, Prelim. Account, Sci. Proc. Eoy. Dubl. Soc., vol. v. p. 179, 1886. 
Sponge (PL I. fig. 16) more or less fusiform or ellipsoidal; with a single oscule at 
one end, and papillose at the other ; eetosome not developed. Mesoderm very small in 
quantity, collenchymatous ; flagellated chambers large, round or elliptical, eurypylous. 
Spicules. — I. Megascleres. 1. Oxea (PI. I. fig. 20), fusiform, anisoactinate, tapering 
(ZOOL. CHALL. EXP. — PART Lxiii. — 1887.) Err 1 
