140 A MONOGRAPH OF THE 



The spicula of the skeleton are unlike those of any other 

 sponge with which I am acquainted. They are curved 

 considerably, and constricted at about once their own 

 diameter from the base, so as to become sub-spinulate ; 

 beyond this constriction they dilate rather suddenly, and 

 are fusiform for about one third their own length, and 

 thence to the apex they are regularly attenuated ; some- 

 times the sub-spinulation is scarcely perceptible, or entirely 

 absent, but the fusiform character appears to be constant. 

 The bases of the skeleton spicula are not immersed in the 

 keratose column, but are firmly cemented to its external 

 surface. They are projected from all parts of it, at angles 

 varying from 10 or 12 to 45 degrees, and the terminal ones 

 form a radiating defensive group, from three to five or six 

 in number, the convex side of the spiculum being always 

 outward. The extreme height from the base of the kera- 

 tose column to the apices of the terminal spicula in two 

 cases measured, was ^th and ^th inch. 



The anchorate spicula are few in number, and are irre- 

 gularly dispersed on the dermal membrane; they are very 

 minute, and a few of them appeared to be palmato-anchorate. 



The growth and development of the pedestals is very 

 interesting. The terminal groups of the large defensive 

 spicula are first developed on the basal membrane in a 

 sessile condition, and the increment of the keratode is from 

 beneath them; they are thus gradually elevated from the 

 basal membrane, the lateral spicula being successively pro- 

 duced in accordance with the necessities of their positions. 



I have obtained this species abundantly from the small 

 reefs of rock exposed at low water opposite the town of 

 Hastings, through the medium of Mr. Henry Ridley, where 

 he states it frequently covers the surface of the sandstone in 

 patches ten or twelve inches in diameter, and I have one speci- 

 men in my collection about seven inches long by four in 

 breadth. Although thus spreading so widely, it does not 

 appear to increase in thickness. However carefully dried, 

 after a time it loses its red colour, and assumes a brown 

 or a dirty green hue. 



A hasty observer may readily mistake this species for 



