256 HYALONEMA (PRIONEMA) AGUJANUM. 
The stout- and short-rayed proximally smooth mon- to pentactine acanthophores 
(Plate 76, figs. 8-16, 31, 32). The pentactine forms (Plate 76, fig. 32) are rare 
and have been found only in var. tenuis, form A. They are very much smaller 
than the others and may perhaps be spicules of another kind. The tetractine 
forms (Plate 76, figs. 8, 10-13) with four fairly equally developed rays are 
frequent in all the specimens. Their rays extend in the same plane and enclose 
angles of 90°. They are usually straight and attenuated towards the end. 
The triactine forms are not nearly so frequent. They are evidently tetractine- 
derivates and differ from the true tetractines only by one ray being much reduced 
or suppressed altogether. Transitions between the tetractines and triactines 
(Plate 76, fig. 10) are by no means rare. The diactine forms (Plate 76, figs. 14— 
16) are frequent. They sometimes possess, besides the two properly developed 
rays, a rudiment of a third ray (Plate 76, fig. 15). Those without such a rudiment 
are either centrotyle and spindle-shaped (Plate 72, fig. 14), or simply cylindrical 
and rather thicker at the ends than in the middle (Plate 76, fig. 16). The mon- 
actines (Plate 76, fig. 31) are rare. They appear as tylostyles. The dimensions 
of these spicules are the following :— 
Only terminally spined, basal spicules with 
5 | 4 | 3 2 1 
Hyalonema —— —___ —— _ —— — 
(Prionema) more or less fully developed rays 
agujanum 
a| % a| 4 al 4 =) [S ss a| % 
B. eee 2 Brel smh 2 Be alee 
Boe | a |Hee la" Bee e | esse 1a oe ee 
wae) ge /GE2| Se | gaP) de | BEB] Be | BEB) Be 
ag2| 32 |8s8| 82 | 888| S32 | 8S3| S2 | asé| Ss 
| 
167- a 230— i 117 
form A| 45 6 240 14-17 205 17-18 390 11-21 194 21 
var. tenwis ———- —_- — > 
140- 275- 570- 
2 5-2 
form B 440 11-28 340 15-20 1400 10-20 190 17 
0Q- = 
var. lata =e 12-14 870 12 
all forms and 140- 230- = 117- 190- 
me LF) —21 
varieties ue G 530 0 tE28 | gro 2? 7°. anne oe aoe 
As the entirely spined short-rayed basal acanthophores are sufficiently 
abundant for proper study and measurements only in the Palythoa, and as only 
