HYALASCÜS SAGAMIENSIS. 91 



The parenchyiiialia are all slender diactins of variable thick- 

 ness. Only exceptionally among the thinner ones do there exist 

 such as show an annular swelling in the middle. Their ends 

 are usually sparsely beset with microtubercles and are sometimes 

 pointed and sometimes rounded. The diactins run either isolated- 

 Iv or combined into long thread-like Ijundles. In the latter case 

 some of them may, on account of their larger size, be distin- 

 guished as the principalia. These are long, slender and gently 

 curved or nearly straight oxydiactins, very gradually tapering- 

 out towards ])Oth fine smooth ends. They may attain a length 

 of 20 mm. or more and a breadth of 120 ii. in the middle. 

 The comitalia are only 10 a. thick or even thinner, showing as 

 usual the same breadth for the greater part of their length. 

 The presence of gradationally intermediate sizes between the 

 principalia and the comitalia clearly indicates the origin of the 

 former simply l)y continued growth from amongst the rank of 

 the latter. Synapticular formation exists nowhere, but we should 

 expect to find it in the very base of the sponge which is not 

 preserved. 



Along the oscular edge there are seen at some places a 

 palissade-like row of needles, projecting free for about half a 

 millimeter or so ; however, it is clear that we have here to do 

 not with special marginalia but simply with the ends of ordinary 

 parenchymalia unnaturally exposed as the result of abrasion. 



The hypoderinaUa (PI. VIL, fig. G) are, mainly at least, 

 moderately large oxypentactins with smooth tapering rays. The 

 unpaired proximal ray, which is straight, may be 2-3 mm. long. 

 The paratangential rays aie shorter, generally measuring 0.9- 

 1.2 mm. in length ; they are always curved to a greater or less 



