74 I. IJIMA : HEXACTINELLIDA. I. 



The sword-shaped oxyhexactin dermalia of the general 

 surface are comparative!}^ small and slender, the ray usually 

 measuring less than 1.5 mm. in length and 7-12,« in breadth 

 near the spicular center. The distal hilt- ray is only 130-180/'- 

 long. Exactly as in E. regain, it gradually tapers distally to a 

 fine or conical point and shows obsolete prickles which stand 

 closely together near the outer end but are isolated and sparingly 

 present on the rest of the ray. The five remaining rays are 

 rough only at the ends. The paratangentials (220-350 /i long) 

 of different dermalia tend to form a rectangular mesh work 

 (meshes about 3 mm. wide) in the depressed areas of the external 

 surface ; towards the summits or edges of the parietal prominences 

 the arrangement becomes irregular. The blade-ray, which pierces 

 the choanosome like a nail, is usually several times longer than 

 the hilt-ray, — occasionally only twice but more often it is nearly 

 ten times as long. 



Unusually large and strong hexactin-dermalia occur, together 

 with others of the more ordinary dimensions, along the cuff-edge 

 as well as on the highest parts of the parietal ledges, especially 

 in conjunction with the bristle-like prostalia already mentioned. 

 In these positions they may attain a size more than thrice as large 

 as the ordinary dermalia. In one specimen measured the greatest 

 axial length was 4.7 mm., of wdiich 1.2 mm. belonged to the hilt- 

 ray, the breadth of the rays near the center being 40^. 'While 

 on the one hand there exist intermediate transitional forms between 

 the large and the small dermalia, some of the former are, on the 

 other hand, more or less deeply situated below the others, so 

 that they appear sometimes not unlike hypodermalia or otherwise 

 assume such positions as seem to justify their being taken for 

 parenchymal oxyhexactins. 



