o2te. THE VOYAGE OF H.M.S. CHALLENGER. 
development. It was the examination of this set of specimens which first convinced 
me that the Stylasteride were Hydroids and not Anthozoans, a fact which I had 
already been led to suspect from the structure observed in the case of a species of 
Astylus obtained from 500 fathoms off the Meangis Islands, and that of a Cryptohelia, 
a short reference to which was given in a paper On the Structure and Relations of 
Certain Corals (Proc. Roy. Soc., No. 64, 1875, p. 64, and* Phil. Trans., vol. elxvi., 
part 1, 1876, p. 116). I have examined also other specimens of Stylasteridee obtained 
by the dredge and trawl of the Challenger in various parts of the world, and a few 
specimens from those obtained by the United States’ dredging expeditions, which have 
been generously placed at my disposal by Mr Alexander Agassiz and Count de Pourtales 
of the Museum of Comparative Zoology of Cambridge, Massachusetts. I have also 
examined specimens of Distichopora preserved in spirits, which I obtained from the 
Museum Godeffroy. 
LITERATURE OF THE SUBJECT. 
The family Stylasteridee was formed by the late Dr Gray in his Outline of an 
Arrangement of the Stony Corals (Ann. and Mag. Nat. Hist., vol. xix. p. 127, 
1847). The family was made to contain the genus Stylaster alone, and was thus 
-characterised :— 
“Coral minutely porous, cells deep, cylindrical, with six grooves, each ending in a 
pore and a central style.” 
MM. Milne-Edwards and Haime placed Stylaster in a sub-family Stylasteraceee, from 
which, however, they excluded Errina and Distichopora, although they included Azohelia, 
which is a Madracis. 
Count de Pourtalés, in his Deep-Sea Corals (Illustrated Catalogue of the Museum of 
Comparative Zoology at Harvard College, No. 4, 1871, p. 33), writes as follows :-— 
“ Professor Verrill first recognised the close affinity of Distichopora, Evrrina, and 
Stylaster (Bull. Mus. Comp. Zool., No. 3, 1864). In his Notes on the Radiata (Trans. 
Conn. Acad., vol. i, 1870) he adopted a suggestion of mine to make a distinct family 
of the Stylasteride, which he places in his sub-order Oculinacea, both of us overlooking 
the fact that Gray had already established it.” 
Pourtalés, struck by the porous nature of the -ccenenchym of the ccenostea of the 
Stylasteridee, and other points in the hard structure which he observed, removed the 
Stylasteride from amongst the imperforate corals, and ranged them next to the Eupsam- 
mide. He fully recognised many strong points of atlinity which rendered the family a 
natural one, but failed to ascertain the true character of the organisms, because he had 
not opportunity of examining their soft structures. 
