OF THE SPONGIAD^E. 267 



FIG. 



shaft is exceedingly slender, measuring at the 

 middle ^o^h of an inch in diameter. The large 

 discal end of the spiculmn is slightly convex ex- 

 ternally, has the margin perfectly entire, and 

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

 form end measured ^th 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. him is found immediately beneath the outer mem- 

 brane of the ovary of Spongilla Broicnii, Bowerbank, 

 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 ^th of an inch, and the 

 height very nearly equalled the diameter. Fig. 

 227 represents a side view of the spiculum show- 

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



NEW FORMS OF SP1CULA FOUND SINCE THE PRECEDING ONES 

 WERE DESCRIBED AND FIGURED. 



228. BISPINULATE. X 175 linear. From Halicnemia 



patera, Bowerbank. Page 15. 



229. TRISPINULATE. X 175 linear. From Halicnemia 



patera, Bowerbank. Page 15. 



230. The normal form of spinulate spiculum from the same 



sponge as the spicula represented by Figs. 228 and 

 229." X 175 linear. Page 15. 



f231. 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 TRIRADIATE, with 

 cylindrical entirely spined radii. X 308 linear. 

 From Dictyocylindrus Vickersii, Bowerbank, MS. 



