72 PROCEEDINGS OF THE NATIONAL MUSEUM vol.81 



of rays. All the rays taper gradually or strongly toward the sharply 

 or conically pointed ends. Except at the base of the rays and on the 

 central node, both of which parts are usually smooth or occasionally 

 thinly microtuberculated, the surface of the rays is beset with numer- 

 ous microspines similar to those on the dermalia. 



Oxyhexasters, represented by normal, hemihexactinic, and some- 

 what less frequently by hexactinic, forms, are numerous in the 

 choanosome and in the ectosome, as well as in the endosome. Nor- 

 mally developed oxyhexasters (fig. 7, /) are present frequently in 

 the ectosome and in the choanosome. In them the center is swollen 

 to a globular node, and the principals are exceedingly short or fre- 

 quently almost obsolete. Two or three slender terminals, which are 

 about half as broad as the principals, are attached to each principal. 

 They are apt to be broken off near the base, as the fragments are 

 found in abundance in the soft parts. In diameter, or axial length, 

 the normal oxyhexasters measure 120/x to 140/x. The hexactinic forms 

 (fig. 7, e) (axial length 160/x) are rarely found and are for the most 

 part aj^preciably larger than those of the hemihexactinic form. The 

 terminals are moderately strong, on the average about 10/a thick at 

 the base and slightly rough. In the hemihexactinic form (fig. 7, c, d), 

 1 to 3 of the 12 extremely short or almost entirely atrophied princi- 

 pals each bear two diverging terminals. These are fairly strong and 

 nearly straight. All the terminals of the oxyhexasters mentioned 

 above are rough on the surface, and in those of the endosome the 

 roughness of surface usually becomes more pronounced toward the 

 base of the terminals, distinctly on account of reverted micro- 

 tubercles. 



There is but one kind of microdiscohexaster. This is fairly com- 

 mon near the gastral surface. It is probably not altogether lacking 

 among the parenchymalia. It is rather small and is spherical in 

 shape, with a diameter of 40/z to 45^0,. The six principals are fairly 

 long, about li/x in length ; their outer ends are somewhat expanded, 

 forming a disklike expansion. There are usually 14 terminals ; fre- 

 quently 10 to each principal. The terminal disks are rather small. 



As regards the spiculation of the smaller specimen (B) herein 

 provisionally referred to H. attenuatus: 



Here the paratangentials of the hypodermal pentactins attain a 

 maximum length of 0.85 mm to 1.4 mm, while the proximal unpaired 

 ray may be 1.7 mm long and 25ju broad. They are shorter and de- 

 cidedly slenderer than in the larger specimen; and further the 

 paratangential is nearly straight to the ends which have an entirely 

 smooth surface. 



Among the dermalia the pentactins occur infrequently and the 

 hexactins very rarely, while they are fairly abundant in the larger 

 specimen. 



