248 A MONOGRAPH OF THE 



genus, notwithstanding a rather close simulation of the 

 structure of its skeleton. If we examine a longitudinal 

 section in water, the comparatively large quantity of sarcode 

 that surrounds the lines of the skeleton would seem to in- 

 dicate its being a Chalina, of a very delicate structure, but 

 in mounting it in Canada balsam, this simulation of fibre 

 entirely disappears, and we find the skeleton spicula very 

 much longer than are observable in any known species of 

 that genus, and it also lacks the symmetrical arrangement 

 of the parts of the skeleton of Chalina. We are, therefore, 

 under the necessity of considering it as an abnormal form 

 of Halichondria. The sponge consists of a single principal 

 stem, an inch and a half in height, and rather exceeding a 

 line in thickness, from which four small simple branches 

 are given off in an irregular manner ; three on one side a 

 little above the middle of the parent stem, and one about 

 half an inch from its base at right angles to the other three, 

 the largest of these being about nine lines in length, with 

 a diameter slightly exceeding half a line. The principal 

 stem of the sponge has lost its natural terminations, the 

 small branches gradually attenuate to rather acute points. 

 From its size, colour, and structure, thus far considered, it 

 might be imagined to be an abnormal form of H. albescens, 

 but the difference in the form and size of the spicula at once 

 forbids this conclusion. Neither oscula nor pores could be 

 detected on any part of its surface. Nearly the whole of 

 the dermal membrane has been destroyed ; a small portion 

 of it in a good state of preservation, was crowded with 

 tension spicula, irregularly and closely felted together on 

 all parts of it ; the spicula differed from those of the skeleton 

 only, in being shorter and much more slender in their pro- 

 portions. The skeleton is slender and delicate in its struc- 

 ture ; the thickest of its lines contains but few spicula, and 

 a great number of them consists of only a single stout 

 spiculum, coated with sarcode. The reticulation has a 

 general tendency of the areas to elongate in the direction 

 of the axis of the sponge, so as to have a faint resemblance 

 to that of the axial cylinder of a Dictyocylindrus. There 

 remained but very slight traces of interstitial membranes, 



