24 Mr. H. J. Carter on the 



type of a division of this family, in wliicli the anastomosing 

 thread-like tibre is solid instead of hollow — a form entirely 

 absent in the " Kalkschwamme " of Hiickel, but one of 

 mucli interest, as I have heretofore shown, in elucidating the 

 structure of some of the fossil Calcispongije, which I hope to 

 still further advance by a description of the following new 

 variety of Leucosolema lacunosa. 



Leucosolenia lacunosa ^ Bk., var. Hillierij Crtr. 

 (PI. I. figs. 1-5.) 



Small, stipitate, erect ; body globular, obconic, rather 

 compressed and turned to one side ; stem cylindrical and 

 long, rather bent upon itself and compressed in its upper 

 part. Body not hollow, but composed throughout of massive 

 clathrous structure; stem solid (PI. I. figs. 1, 2). Colour 

 pale yellowish white. Consistence firm, resilient in the 

 head, hard and unyielding in the stem. Clathrous struc- 

 ture or network (fig. 2, g) consisting of a mass of reticu- 

 lated anastomosing thread-like tube (fig. 2,/) issuing from 

 the stem in several divisions (fig, 2, t/), and terminating 

 in the summit by a central dilatation into which the neigh- 

 bouring branches of the reticulated structure are gathered 

 together centripetally (fig. 3, Z»), finally opening by a single 

 naked aperture more or less protruded, which is the osculuni 

 (figs. 2 b and 3 a) . Pores minute, in the wall of the tubular 

 structure. Stem consisting of a compact solid mass of spicules, 

 compressed in its upper part, which is expanded scopiformly 

 into the " divisions " mentioned (fig. 2, d), which, being solid 

 like the stem at first, pass respectively by transition into the 

 tubular form which characterizes the structure of the body 

 (fig. 2, a), terminating below in a root-like expansion which 

 is fixed to the object on which the sponge may be growing 

 (fig. 2, e). Structure and composition of the wall of the 

 reticulated fibre the same as that of Clathrina coriacea just 

 mentioned, only the meshes of the network are elongated 

 vertically, which of course is followed in direction by the 

 branches of the tubular thread, i. e. from the stem to the 

 summit. Spicules of three forms, viz.: — 1. Triradiate, equi- 

 angular, inequiradiate, rays straight, smooth, rather obtusely 

 pointed, the longest, which in the largest of these spicules is 

 three or four times longer than either of the other two, 

 directed backwards (fig. 4, a) ; the rest infinitely variable in 

 size generally and in the unequal length of their rays, some 

 nearly cquiradiate (fig. 4, h) ; longest ray of the larger tri- 

 radiates (fig. 4, a) about 48-6000ths inch long by 2-t)000ths 

 inch broad at the base. 2. Linear, acerate in appearance, but 



