REPORT ON THE TETRACTINELLIDA. 
CXXVll 
Phylogeny of the Sigmatophoha. 
Tetillidse Samidse 
Craniella 
Cinachyra Chrotella 
I 
Tetilla Samtis 
Suborder II. ASTROPHORA, SoUas. 
Asterophora, Sollas, Encyclopaedia Britannica, vol. xxii. p. 423, 1887. 
Choristida in which one or more of the microscleres is an aster. 
Demus I. Steeptastrosa, n. n. 
Spirasfrosa, Sollas, Encyclopaedia Britannica, vol. xxii. p. 423, 1887. 
Astrophora in which one of the microscleres is a spiraster, or when this is not the 
case one of the megascleres is a calthrops. 
The name originally given to this group, Spirastrosa, is too similar to that adopted 
by Ridley and Dendy for a Monaxon family, Spirastrellidse, and for the sake of distinction 
Streptastrosa is now substituted. 
Family I. Theneida:, Sollas. 
Group Theneanina, Carter, Ann. and Mag. Nat. Hist., ser. 5, voL xi. p. 354, 1883. 
Theneidx, Sollas, Sci. Proc. Roy. Dubl. Soc., vol. v. p. 178, 1886. 
History. — This family is founded on the genus Thenea, Gray, who evidently had 
some notion of the value of the spiraster in classification ; a point that was subsequently 
insisted on by myself both as distinguishing Thenea from Stelletta and as allying it with 
Pcecillastra.^ It was next made use of by Garter, who chose it as the distinctive 
character of a subfamily, which he named Theneanina, including in it the genera Thenea 
and Pcecillastra. The group is here regarded as of family rank. 
Definition. — Streptastrosa in which the microscleres are spirasters or amphiasters, 
and oxyasters or microxeas. 
The ectosome never forms a cortex. The mesoderm is a collenchyma. The chamber- 
system is eurypylous. 
The family cannot be defined by the spiraster alone, as this is also present in the 
Pachastrellidae, which no doubt are very closely allied to the Theneidse, bearing some- 
what the same relation to them that the simpler genera of Tetillidse do to the more complex. 
* Sollas, Ann. and Mag. Nat. Hist., ser. 5, vol. ix. pp. 434, 443. 
