REPORT ON THE HEXACTINELLIDA. 77 



In opposition to the opinion which has been expressed by several authors, e.g., 

 Marshall/ to the eflfect that Euplectella cucumer is not specifically distinct from Euplec- 

 tella aspergillum, I must point to the following essential difi"erences. Whilst Exiplectella 

 aspergillum has the form of a bent tube, which becomes wider towards the upper 

 extremity, Euplectella cucumer consists of a perfectly straight, bellied tube, devoid 

 both of the externally projecting ridges and of the cuff on the upper margin. The 

 regularity of the arrangement of the round parietal apertures, which is frequently inter- 

 fered with in Euplectella aspergillura, is everywhere manifest in Euplectella cucumer. 

 The fusion of the skeletal spicules which appears in all parts of the tube of Euplectella 

 aspergillum soon after the attainment of its full size, has taken place in this obviously 

 old specimen of Euplectella cucumer only to a very limited degree in a few regions. 



It thus appears to me that (on the whole) Euplectella cucumer is more nearly related 

 to Euplectella suherea than to Euplectella aspei'gillum. From Euplectella suherea, 

 however, it may be distinguished first by the compact sieve-plate, consisting of strong, 

 firmly united spicules, and secondly, by a character which Owen noted, and which Carter 

 subsequently announced as a distinctive peculiarity, — the possession of strong hexacts, 

 1 to 2 cm. in length, regularly distributed in such a way that one always occurs in 

 the middle space between every four adjoining parietal gaps, with its strong distal ray 

 projecting freely from the summit of the raised arching of the outer wall. 



From such considerations I believe I am justified in maintaining that Euplectella 

 cv^umer, Owen, is an independent species. 



4. Euplectella jovis, Oscar Schmidt (PI. VI. figs. 4, 5). 



According to Oscar Schmidt's account Euplectella jovis — found in the Gulf of Mexico, 

 in 423 fathoms in the neighbourhood of St. Lucia, and in 416 fathoms in the vicinity of 

 Granada — agrees in many points with Euplectella suherea, Wyville Thomson. The 

 straight tube, which extends to a length of 50 cm., is provided with a basal tuft and a 

 terminal sieve-plate ; but the external ridges are absent. A projecting wreath of spicules 

 surrounds the sieve-plate. The round parietal gaps are arranged in spiral rows, though 

 not quite regularly (PI. VI. fig. 4). On the inferior extremity 0. Schmidt found a trans- 

 versely placed inferior sieve-plate which divided the inferior conical portion of the tube, 

 which was filled with mud, from the principal vital portion. 



As the spicules never become fused the tube remains soft and flexible. 



The intersections of the longitudinal and transverse strands of fibres forming the 

 c^uadrate lattice-like network are here also principally supported by the mutually apposed 

 tangential rays of the strong pentacts, whose distal radial ray projects freely outwards, for 

 a distance of 1 or 2 cm. beyond the surface. An intersection of the fibrous lattice- work, pro- 



1 Zeitschr.f. iviss. ZooL, Suppl.-Bd. xxv. pp. 148, 209. 



