28 PROCEEDINGS OF THE NATIONAL MUSEUM vol.81 



breadth at the base is nearly the same in all, 20^. to 40/;i. All the raj^s 

 are smooth on the surface and gradually attenuated toward the coni- 

 cally pointed end. 



Of the microsclere parenchymalia I shall first describe the oxy- 

 hexactins (fig. 3, /, g) . These occur abundantly in varying numbers 

 in different regions of the sponge and measure 120^ to 150ju in di- 

 ameter. Their rays are fairly stout, quite smooth, sharply pointed, 

 and extremely curved at the end. Of the curved tangential rays, I 

 have found two kinds : Some are curved away from their fellow 

 at the end, while others are directed toward one another on one 

 side. I have found the former condition much commoner than 

 the latter. In the subdermal regions, these oxyhexactins are fre- 

 quently arranged in lines and groups of several. Other than in these 

 regions, I found these spicules also in the subgastral region and in 

 the parenchyme, as well as in the wall of the excurrent canals, 

 where they were distributed both in groups and separately. Besides 

 these oxyhexactins, oxypentactins of the same features are found in- 

 frequently intermixing with the former. 



Oxypentactinic dermal pinnies (fig. 3, a) cover the external sur- 

 face in great numbers. Their four basal raj^s, which form a rectan- 

 gular cross, are of medium thickness and measure 6/x at the base and 

 45/x in length ; terminally they are pointed and irregularly roughened. 

 The free radial ray is on the average 200;^ long, smooth in the proxi- 

 mal third, uniformly attenuated toward the pointed end, and in the 

 distal two-thirds irregularly covered with rather short, slightly di- 

 vergent spines. The spines attain their greatest length at the middle 

 or somewhat below the distal spined parts of the ray; above and 

 below they gradually decrease in size. 



The canalar pinules (fig. 3, 5) are nearly similar; the distal ray 

 being a little shorter than that of the dermal pinules, instead of 

 having a longer paratangential ray, measuring 60|U, in length. They 

 occup}^ the walls of the larger incurrent canals but do not stand 

 nearly so close together as the dermal pinules on the external surface. 



The gastral pinules (fig. 3, a) are entirely similar to those of the 

 derm. 



Macramphidisks (fig. 3, c) are found infrequently on the dermal 

 membrane itself and are entirely absent in the hypodermalia and in 

 the internal parenchyme. They attain a considerable size, 350/x or 

 more in length. The shaft is either smooth or covered with a few 

 irregularly distributed small tubercles, and measures 30/i, in width 

 at the center. The terminal disks are lOOjit long and 160/x broad, 

 nearly semicircular, and somewhat expanded proximally and nar- 

 rowed distally at the flattened ends. They have 8 to 9 marginal 

 teeth, 100|U, long, which terminate with somewhat lancet-shaped 

 points. 



