338 ANATOMY AND PHYSIOLOGY 



Fia. 



64. Rectirvo-dentato-birotulate. — From soundings in 



the Indian Ocean, 2200 fathoms. Most probably 

 from another imknown species of Hyalonema. 

 X 308 hnear. 



65. InFLATO - FUSIFORMI - ACERATE ASCENDINGLY HEMI- 



spiNous. X 108 Hnear. — Hyalonema mirahilis. 

 Gray, British Museum. Projected in abundance 

 from the dermal surface of the sponge ; the smooth 

 basal half being immersed in the tissues beneath 

 the dermal membrane and the spinous distal por- 

 tion being projected beyond it. Purely external 

 defensive. 



66. AtTENUATO-ACU ATE, ENTIRELY SPINED. YxGm.I>ictyO- 



cylindrus ventilabrum, Bowerbank. X 260 linear. 

 Internal defensive. Page 29. 



67. ACUATE, ENTIRELY AND VERTICILLATELY SPINED. — 



Prom an undescribed sponge, X 400 linear. Inter- 

 nally defensive. I have found it in two distinct 

 species of sponge from the West Indies. In one 

 it is irregularly dispersed, and in the other it is 

 collected into radiating groups. See Figs. 289, 

 290, Page 30. 



68. Cylindrical: entirely and vertioillately 



SPINED. X 400 linear. — I am not acquainted 

 with the sponge whence this beautiful spiculum 

 came. I found it in the refuse matter from the 

 base of a specimen of Oculina rosea, from the 

 South Seas. The shaft of the spiculum, from end 

 to end, has equidistant rings of single series of 

 acute conical spines, and the base and apex of the 

 spiculum are each equally crowded with spines. I 

 have arranged it as a defensive spiculum, from its 

 near approximation to the characters of the spicu- 

 lum last described ; but it is subject to the doubt 

 whether it may not ultimately prove to have be- 

 longed to the skeleton. Page 30. 



