SPICULA FROM SPONGES. 191 



placed in an annular form (Plate IV. No. 2), and another in which the 

 spicula exhibit many curious forms ; within the circle may be seen 

 one spiculum of remarkable beauty, being of large size, rounded at both 

 ends, and slightly bent ; its outer surface is covered with rows of tuber- 

 cles of circular figure, which project some little distance beyond the 

 free margin. 



In HalicJiondria from New Zealand there are found some with 

 the spicula of the acuate form covered with spines, blunt at one end 

 and sharp at the other ; the spines are small, without order in their 

 situation, but greater in number at the middle. 



In the genus Pachymatisma some spicula are sharp at one ex- 

 tremity and expand into two points at the other expando-binate ; 

 they are large, and their purpose is that of connecting the crust and 

 the fleshy matter compactly together. The P. Johnstonia spicula are 

 sharp at one end and expand into three points at the other expando- 

 ternate ; arranged at angles at 45 to the other part of the stem 

 (Plate IV. No. 7); there is also in this kind a variety having spicula 

 sharp at one end and expanding into three branches at the other, each 

 of which again divides into two dichotoino-expando-ternate kinds. 



In the genus Tethea there are spicula having hooks at both ex- 

 tremities bi-recurvo-ternate : at one end they are not so large or so 

 numerous as at the other ; the stem is a little spinous. 



In TetJiea Lyncurium the ends of the branches of the spicula are re- 

 curved, forming two, three, or four hooks, which serve to anchor the 

 crust to the soft central fleshy part ; their term is recurvo-binate, 

 ternate, &c. Of the recurvo-ternate we give a specimen from a species 

 of Pachymatisma. (Plate IV. No. 6.) 



Among the genus Grantia, Geodia, and Levant sponge, are found 

 spicula of a large size, radiating in three directions triradiate. In 

 the Levant specimen, a central communicating cavity can be distinctly 

 seen. Some Smyrna "sponge, and a species of Geodia, have four rays 

 quadriradiate. 



There are spicula in P. Johnstonia and Geodia that have as many 

 as ten rays multiradiati ; they vary in number. (No. 12.) 



In some species of Tethea the spicula consist of a central sphe- 

 rical body, from which short conical spines proceed stellate spi- 

 cula. (Plate IV. No. 4.) These are also found in some of the genus 

 Geodia. 



Branched spicula, some covered with spines, have been taken from 

 sponge brought from Ceylon ; and from sponge from the same place, 

 spicula more or less curved curvate. 



