314 



ERYLUS CALICULATUS. 



average proportion of length to breadth to thickness is 100:95:15. In the 

 reniform aspiclasters (Plate 6, figs. 21, 22; Plate 7, figs. 38-41), which are other- 

 wise similar to the broad-oval to circular ones, the margin is incised at a point 

 usually lying on one of the broader sides. This incision may be quite insigni- 

 ficant (Plate 7, fig. 39) or it may extend far into the interior of the spicule 

 (Plate 6, fig. 21). The reniform aspidasters have similar dimensions to the 

 l^road-oval or circular ones, but are somewhat narrower, some not more than 

 63 /t broad. The surface of the adult aspidaster is covered with short, truncate, 

 protruding rays, 1.8-4 [x thick. These rays bear terminal verticils of lateral 

 spines, and usually also some spines arise from their apical faces. The number 

 of protruding rays is very variable. On some aspidasters (Plate 6, fig. 20; Plate 

 7, figs. 32-35, 38-40; Plate 8, figs. 15, 16) they are few and far between, in 

 others (Plate 6, fig. 19; Plate 7, figs. 36, 37, 41; Plate 8, figs. 17-20) very 

 numerous and, although usually distributed rather irregularly, nowhere very 

 far apart. 



The youngest stages of the aspidasters (Plate 7, fig. 31 ; Plate 8, fig. 1) 

 appear as chscs composed of slender rays radiating from a common centre. 

 The great majority of these rays are as long as the radius of the disc, lie nearly 

 in one plane, and extend from the centre to the margin of the disc. A few are 

 much shorter, and these are situated obliquely to the plane of the disc occupied 

 by the long raj^s (Plate 8, fig. 1). These ray-aggregations grow in the same 

 way as in Erylus rotundus, described in detail, p. 306, and become smooth discs 

 (Plate 6, fig. 22), on the surface of which protruding rays later make their appear- 

 ance. It seems, a priori, probable that the aspidasters with few protuberances 

 (Plate 6, fig. 20; Plate 7, figs. 32-35, 38-40; Plate 8, figs. 15, 16) are young 

 forms which later, by the accession of further protul)erances, are converted into 

 the aspidasters with numerous protruding rays (Plate 6, fig. 19; Plate 7, 

 figs. 36, 37, 41; Plate 8, figs. 17-20). Since, however, the protrucUng rays of the 

 aspidasters with but few of them seem to be on the whole larger than those of 

 the aspidasters with many of them, this is somewhat doubtful. 



This sponge was caught with the tangles on the northeast coast of Plawaii, 

 Station 4062, Kauhola Light, S. 69° 15', E. 6.9' on July 18, 1902; depth 152- 

 206 m. (83-113 f.); it grew on a bottom of coral, volcanic sand, shells, and 

 Foraminifera. 



The structure of the canal-system and the spiculation of this sponge clearly 

 show that it belongs to Erylus. From all the species of this genus previously 

 described it differs considerably by the partly broad-oval to circular, partly 



