110 
THE VOYAGE OF H.M.S. CHALLENGER. 
(4) Retepora imperati. Busk, M.S. (Pl. XXYI. fig. 9). 
Retepora eschara marina , Imperato, 1559, p. 821. 
Retepora cellulosa, a. (pars), Auctt. 
Millepora foraminosa, Ell. and Soland., p. 138, pl. xxvi. fig. 2. 
(1) Retepora elongata, d’Orb. and Smitt, var. 
Character. — Zoarium of large size, repand, flexuose, widely infundibuliform. 
Fenestra; elongate, rhomboidal, narrow, about 0 //- 085 long. Dorsal surface of trabeculae 
smooth and glistening. Zocecia distinct, ovoid, separated by raised septa ; anterior 
surface granular. Orifice suborbicular, slightly sinuated in front. Peristome thin, much 
raised on the sides, where it often forms a point. No labial fissure, or suboral pore, or 
oral avicularium. Ocecia very conspicuous, subcucullate (fig. 9 d). Anterior avicularia 
sparse, and placed only on the older zocecia, rostriform and projecting directly forwards ; 
mandible long, acute, with the point curved forwards. Dorsal avicularia spear-shaped, 
numerous, irregularly distributed ; one usually of larger size than the others at 
the lower angle of each fenestra. Operculum rounded oval, the muscular insertions on 
each side above the middle. 
Habitat. — Station 75, lat. 38° 38' N., long. 28° 28' 30" W., 450 fathoms, volcanic 
mud. Port Praya, St. Iago, Cape Yerde Islands, 100 to 120 fathoms. 
[Mediterranean, H.M.S. “ Porcupine,” M‘Andrew]. 
It is a remarkable circumstance that, so far as I am aware, this very well marked and 
most conspicuous species should have hitherto, as it would seem, escaped distinct recogni- 
tion, and the more so as it is probably abundant enough in the Mediterranean, forming, 
in fact, the bulk of the forms of Retepora collected on the voyage of the “ Porcupine ” in 
that sea, where, as is well known, three or four other species also occur, all of which 
have been often confounded under the common appellation of Retepora cellulosa. 
But reference to the coarse, though sometimes very graphic, figures of the older 
writers, and especially to that contained in Imperato’s work, will suffice to prove that in 
many, if not most cases, they have had the present form before their eyes. 
It has, however, unfortunately happened that most later authors since Ellis have 
apparently only been acquainted with the two common northern forms, whose general 
similarity with that figured by Dr. Solander has led to their being confounded with it, 
although most have recognised a certain difference of habit, leading to the suspicion that 
the species might be distinct. 
In the British Museum Catalogue (1852), the account of the species designated 
Retepora cellulosa was drawn up from specimens in Dr. Johnston’s collection, 
amongst which it so happened that I noticed only the form so named, and another 
described by Mr. King as Retepora beanianci. The former may probably have been 
intended by Dr. Johnston, under the name of Retepora reticulata, but the reten- 
