cxxx 
THE VOYAGE OF H.M.S. CHALLENGER, 
occupying the usual position in the ectosome and the calthrops occurring in the 
choanosome. Anatrisenes are absent. The microscleres are spirasters, plesiasters or 
oxyasters, and microxeas. 
History . — The Sponge on which Bowerbank founded this genus was named by him 
Normania crassa, it was dredged off Shetland by the Eev. A. M. Norman {vide p, 98). 
First mentioned in the British Association Report {loc. cit.), it was afterwards fully 
described in the Monograph of the British Sponges {loc. cit.). In 1878 Carter^ stated 
that Ecionema compressa, Bowerbank, 1866, Hymerdacidon placentula, Bwk., 1874, 
and Normania crassa, Bwk., 1868, are identical species, and only varietally different from 
Thenea muricata. Specimens placed in my hands by the Rev. Dr. Norman for the 
purpose, enabled me to confirm this statement as regards the identification of the first 
three species, but not as regards the closeness of their association with Thenea muricatad 
This was clearly an error, as Norman^ has also pointed out, and as Carter^ has since 
admitted. 
Since the first three species are identical it becomes necessary to make a choice of 
generic and specific names. And first as to the genus. Hymeniacidon can at once be put 
out of court ; whatever else that genus may be it does not belong to the Tetractinellida, 
There remain Ecionema and Normania ; Carter, on the ground that Ecionema has 
precedence, declares for it, I think, somewhat hastily ; the genus Ecionema was defined 
by Bowerbank® in 1864, and the species Ecionema acervus, Bwk., specially assigned to 
it as the type. The genus cannot therefore be used to include species generically 
different from Ecionema acervus. Now this species, as we know from Bowerbank’s® 
descriptions with full illustrations given later, does not even belong to the ' family 
Theneidse ; it is plainly a member of the Stellettidse, and stands there as the type of the 
genus Ecionema. 
Ecionema therefore is not available as a generic name for Normania crassa, 
Hymeniacidon placentula, and Ecionema compressa; and Normania alone remains with 
a claim ; I should have much preferred to retain this as connecting Norman’s name with 
the Sponges, in the investigation of which he has rendered such invaluable assistance ; 
but it appears to have been preoccupied ; true, Bowerbank remarks that Brady’s genus 
Normania, which has precedence, cannot stand, but this makes no difference, since 
according to convention, a discarded name which has ceased to be used for one species, or 
genus, cannot be applied to another, otherwise the door would be opened to confusion. 
I therefore propose to rename the genus Pcecillastra. 
^ Carter, Ann. and Mag. Nat. Hist., ser. 5, vol. ii. p. 174. 
^ Sollas, Ann. and Mag. Nat. Hist., ser. 5, vol. ix. p. 433, 1882. 
® Bowerbank, Mon. Brit. Spong., vol. iv. p. 29, 1882. 
* Carter, Ann. and Mag. Nat. Hist., ser. 5, vol. xi. p. 359, 1883. 
® Bowerbank, Mon. Brit. Spong., vol. i. p. 173, 1864. 
® Bowerbank, Froc. Zool. Soc. Lond., p. 322, pi. xxx. figs. 1-6, 1873. 
