238 
THE VOYAGE OF H.M.S. CHALLENGER. 
directed at right angles to the cortex, which they support by their cladomes ; and of 
oxyasters, which commence at the chonal sphincters where the microstrongyles cease 
to appear. 
Spicules. — I. Megascleres. 1. Oxea, fusiform, sharply pointed, occasionally 
strongylate at one or both ends, 1’06 to 1’24 by 0'035 mm. 2. Dichotrisene, rhabdome 
conical, sharply pointed, 0*556 by 0'0516 mm. ; protocladi from 0*127 to 0*143 mm. long; 
deuterocladi from 0*175 to 0*368 mm. long. 
II, Microscleres. 3. Sterraster, disciform, thin, circular or elliptical in outline, actines 
forming radiating rounded ridges on the more or less flat face, surface granulated ; 0*084 
to 0*106 by 0*077 mm,, and 0*015 mm. thick. 4, Oxyaster,no definite centrum, actines 
slender, conical, smooth, varying in number from three to twelve, a single actine 0*023 
mm. in length, 5. Microstrongyle, fusiform or cylindrical, centrotylote or not, surface 
roughened, 0*028 by 0*0035 mm. 
Colour . — Black internally, owing to the presence of pigment-cells in the cortex. 
Habitat . — Lesina, Adriatic (0. Schmidt) ; north-west Spain (Saville Kent). 
Remarks. — The measurements of the spicules were obtained from a type-slide in the 
British Museum, and checked by others mounted by myself from a dry specimen kindly 
presented me by Professor von Graff. There is another slide labelled Stelletta dis- 
coyihora, 0. S., Florida, amongst those presented to the British Museum by Oscar 
Schmidt ; but its spicules appear to more closely resemble those of Erylus euastrum, 0. 
Schmidt. A specimen referred to Erylus discophorus by Saville Kent, who dredged it 
off the north-west coast of Spain, occurs in the Kent Collection of the British Museum 
(No. 21, registered No. 72. 5. 4). This I have not examined. 
Erylus mammillaris (0. Schmidt). 
Stelletta mammillaris, 0. Schmidt, Spong. Adriat. Meeres, p. 48, pi. v. fig. 1, 1862, and 
Suppl., iii. p. 20, 1868. 
Erylus mammillayis. Gray, Proc, Zool. Soc. Loud., p. 549, 1867. 
Sponge. — Growing from a widely extended base into a number of mammillary lobes, 
each of which bears a single large oscule at the extremity. Pores each the single 
opening of an incurrent chone. Cortex thin. Microstrongyles occur throughout the 
choanosome as well as beneath the epithelium of the cortex. 
Spicules . — I. Megascleres. 1. Oxea, curved or sinuous, 1*5 by 0*032 mm. 2. 
Dichotrisene, rhabdome conical, oxeate, 0*716 by 0*044 mm.; protocladi 0*09 by 0*036 
mm.; deuterocladi 0*09 mm. long. 
II, Microscleres. 3. Sterraster, ellipsoidal, the ends of the actines covered with 
rounded granules; 0*106 by 0*043 by 0*032 mm. in diameter, or less elongated and 
wider, 0*0775 by 0*0516 mm. 4. Choanosomal spheraster, centrum small, actines conical, 
