ART. 12 HEXACTIXELLID SPONGES OKADA 15 



and sometimes much slenderer, and are covered with numerous micro- 

 spines irregularly distributed on the surface. 



The microuncinates, which are nearly similar to those occurring in 

 SeHcolophus re-jiexus Ijima, are fairly abundant, are 4/^, broad at the 

 center, and are spindle-shaped, with both ends sharply pointed and 

 the surface quite smooth. 



Genus SERICOLOPHUS Ijima, 1901 



SERICOLOPHUS KEFLEXUS (Ijima) 



Hijalonenia reflex-um Ijima, Zool. Auz., vol. 17, p. 336. 1894. 

 Sericolophus reflexus Ijima, Journ. Coll. Sci. Imp. Univ. Tokyo, vol. 15, p. 128, 

 1901 ; /gffeOfira-Expeditie, vol. 6, pp. 26-28, 1927. 



There are 13 specimens of S. i^eflexus in the collection. The differ- 

 ence between the dermal and gastral pinnies is not only in the state 

 of the spines on the distal ray, as described by Ijima from the speci- 

 mens from Sagami Sea, but also from my observation it is found 

 in the dimensions of corresponding parts of the spicules. The distal 

 ray of the gastral pinule averages 160;^ to 260/i in length, 14/i, broad 

 at its base, and the basal crossing rays attain a length of 240/x and 

 are 8/^ broad at the base. The dermal pinules, though somewhat 

 smaller than those of the tj^pe specimen, have a distal ray 120ju, to 

 160/i, in length and basal rays TO^u, to lOOyu. long. The hexactinic 

 dermal pinules are infrequently found in the ectosome of several 

 specimens. The paratangential ray is TO/a to 90/a long and terminally 

 pointed. The proximal ray is 90/x long and the distal pinular ray 

 136;u long. 



The parenchymal microxyhexactins are much slenderer and their 

 prickles are not so prominently developed as those of Siboga speci- 

 mens of this species. From my observations of the preparations of 

 the Sihoga specimens and those from the Sagami Sea it is evidently 

 exhibited that the parenchymal oxyhexactins may vary considerably 

 in size and shape. The Sihoga specimens have more robust and 

 larger rays, beset with prominent prickles on the surface, while the 

 present specimens have distinctly slenderer rays and very slightly 

 developed prickles. The Sagami Sea specimens have the spicules 

 intermediate in size. 



Besides the microxyhexacts, which occur abundantly in the type 

 specimen as well as in the present ones, there exist other micropen- 

 tacts, which are mostly distributed in the wall of the excurrent 

 canals and in the parenchyme, intermixed with the microxyhexacts. 

 The spicule is provided with an unpaired distal ray IOO/a to 180/x, long 

 and with a paratangential basal ray 190/x to 320ja long, the surface 

 of which is slightly roughened. Frequently the basal rays are curved 

 to certain directions near the distal ends. 



