SPONGES COLLECTED IN PORTO RICO. 
381 
Fig. 25. 
16 17 
15. Sanidaster. 
16. Sigma. 
17. Sigmaspire. 
18. Sphsrohexaster. 
19, 20. Two forms of sphsraster. 
21. Spherule. 
22. Toxa. 
Spiculo- fiber. Tract of uniaxial spicules united by spongin to form a fiber, becoming, when spicules are 
reduced in number, a horny fiber containing spicules. 
Spiraster. Microsclere consisting of a spirally bent axis, bearing spines on its outer surface. 
Spongin. The horny material 
uniting spicules to- 
gether, or (as in the 
Keratosa) constitut- 
ing the skeleton. 
Sterraster. Euaster with nu- 
merous rays, which 
become soldered to- 
gether. Fig. 23. 
Streptaster. A comprehensive 
term applied to asters 
in which the rays proceed from an axis, and not from a center. 
Strongyle. A uniaxial spicule in which both ends are rounded, but not swollen. Fig. 27. 
Strongyloxea. A uniaxial spicule with one end simply rounded off, the other pointed. Not, in general, 
distinguishable in shape from the style 
(fig. 28) . According to the terminology 
of Sollas (1888) the term is restricted 
to aiactinal spicules, style being used for 
monactinal spicules of approximately 
similar shape. But in many cases the 
‘ ‘ point of origin ’ ’ of the spicule can not 
be made out. Where I employ the term 
it is to facilitate reference to previous 
important descriptions. 
Style or stylus. A uniaxial spicule with one end simply rounded off, the other pointed. Fig. 28. 
Subdermal cavity. A comparatively extensive chamber just beneath surface, opening to exterior either 
directly through the pores or by means of short canals. A peripheral enlargement of the 
inhalent canal system. 
Subtylostylus. A tylostylus in which the enlargement at one end (head) is very slight. 
Tetraxon. Spicule in which the rays develop 
W 
23 c 
23a 236 
23. Stages in development of Sterraster: 
6, next condition; c, perfect spicule. 
24. Trichodragmata. 25. Spiraster. 
24 25 
a, youngest stage; 
< 
26 
c 
D 27 
c 
o 
28 
29 
C 
O 30 
along four axes. 
Tornote. A uniaxial spicule in which both 
ends are abruptly pointed. Fig. 26. 
Toxa. A bow-shaped microsclere. Fig. 22. 
Trisene. A tetraxon in which a ray, distin- 
guished as the shaft or rhabdome, 
bears at one end three other rays, 
the dadi. The cladi together con- 
stitute the cladome. Forms of the 
triscne are shown in figs. 1,8,13. Dis- 
tance between the ends of two cladi 
is the chord, ch. — cli. in figs. 1 and 
13. Perpendicular distance from the 
origin of the cladome (point where 
cladi spring from rhabdome) to the chord, is the sagitta (line s in figs. 1 and 13) . 
Trichodragmata. Hair-like spicules in bundles. Fig. 24. 
Tylostylus. A uniaxial spicule pointed at one end, swollen at the other. Fig. 29. 
Tylote. A uniaxial spicule swollen at both ends. Fig. 30. Used as an adjective with respect to any 
spicule ray, it implies that the ray is swollen or knobbed at the end. 
Uniaxial. Term applied to a spicule in which growth proceeds along only one axis. Spicule ( mongxon ) 
is thus rod-like, though it may be straight, or somewhat curved, or even bent. Figs. 9, 10, 26, 
27, 28, 29, 30. 
Uniserial. Arranged in one row. 
26. Tornote. 
27. Strongyle. 
28. Style. 
29. Tylostylus. 
30. Tylote. 
