OF THE SPONGIAD^. 267 



Fig. 



shaft is exceedingly slender, measuring at the 

 middle 55500th of an inch in diameter. The large 

 discal end of the spiculum is slightly convex ex- 

 ternally, has the margin perfectly entire, and 

 is i— th of an inch in diameter. The small lenti- 

 form end measured Bosoth of an inch in diameter, 

 and the total length of the spiculum is ^th of an 

 inch. Fig. 225 represents the inner surface of the 

 rotula. Pages 60, 137. 



226. Umbonato-scutulate. X 660 linear. — This spicu- 



227. lum is found immediately beneath the outer mem- 

 brane of the ovary oiSpongilla JBrownii, Boviferbank, 

 from the River Amazon. The form is truly that 

 of a little shield, the lower surface being concave, 

 while the upper one has a corresponding degree of 

 convexity, and the umbo projects from its centre in 

 the shape of a small cone. The diameter of an 

 average-sized one is T^t\i. of an inch, and the 

 height very nearly equalled the diameter. Pig. 

 227 represents a side view of the spiculum show- 

 ing the length and form of the umbo. Page 60. 



NEW FORMS OF SPICULA FOUND SINCE THE PRECEDING ONES 

 WERE DESCRIBED AND FIGURED. 



228. BispiNULATE. X 175 linear. — ^Prom Salicnemia 



patera, Bowerbank. Page 15. 



229. Trispinulate. X 175 linear. — Prom Halicnemia 



patera, Bowerbank. Page 15. 



230. The normal form of spinulate spiculum from the same 



sponge as the spicuk represented by Pigs. 228 and 



229. X 175 linear. Page 15. 

 (231. Undeveloped forms of spinulate, bispinulate, and 

 \ 232. trispinulate, from the same sponge as the three pre- 

 (233. ceding figures. X 175 linear. Page 15. 

 234. Spiculated inequi-angulated teiradiate, with 



cylindrical entirely spined radii. X 308 linear. — 



Prom JMctyocylindms Fickersii, Bowerbank, MS. 



