ART. 12 



HEXACTINELLID SPONGES OKADA 



111 



diameter, with a distinct, quadrangular central node, which is 8ja to 

 lO/i across. 



The principals are slender and smooth on the surface. They are 

 much shorter, about half or more of the length of the terminals, 

 which measure about 16/a long. There are two to four terminals to 

 each principal. The tuft is also gently curved near the end. The 

 terminal disks are also much smaller and are pinheadlike in shape. 



Remarks. — The distinguishing characters of the present species 

 are: (I) Two kinds of discoctaster are present; the larger one meas- 

 ures 190;u, to 210/A in diameter and is not provided with a distinct 

 quadrangular central node, while the smaller one measures OO/x and 

 has a very regular, quadrangular central node. (2) There are three 

 kinds of normal oxyhexasters, differing in dimensions, in degree of 

 divergence of the terminals, and in the development of the principals. 



RHABDOCALYPTUS AUSTRALIS Topsent 



Rhahdocalyptus australis Topsent, Result. Voy. S. Y. Belgica, Zoologie, Spong- 

 iaires, p. 37, pi. 2, figs. 5, 6, pi. 4, figs. 14^21, pi. 5, fig. 1, 1901. 



Two complete specimens were obtained from the same station, 

 together with Rhahdocalyptus horealis. Specimen A is larger than B, 

 and is an elongate, tubular, or vaselike sponge, slightly and irregu- 

 larly compressed laterally. It is about 68 mm long, 19 mm broad 

 in the middle, and considerably tapered at the lower end, which 

 measures 13 mm broad. The upper truncated end of the body is 

 occupied by an oval-shaped osculum, measuring 10 mm in diameter. 

 The wall is about 2 mm thick in the middle, gradually becoming thin- 

 ner toward the oscular edge, and is thinner than that of the second 

 specimen. Over the entire external surface, except near the inferior 

 part of the stock, there arise pentactinic prostal pleuralia. In the 

 upper part of the body they are finer and much shorter than those 

 situated lower down. Along the oscular edge the cliactinic prostal 

 marginalia project straight upward, the exposed portion attaining a 

 length of 7 mm. 



Specimen B is very small, measuring about 13 mm in diameter. 

 It retains a barrellike shape, a cross-section of the body being approx- 

 imately circular. It possesses a small circular osculum 4 mm in di- 

 ameter. The body wall is very thick, attaining a thickness of 4 mm 

 ^t the thickest part of the body. Both the prostal marginalia and 



Table 23. — Record of specimens of Rhabdocalyptus australis 



