PORIFERA. HI. 



85 



spined, o-/j—crj4""", not distinctly divided into' two groups; the dermal spicules somewhat fusiform, 

 polytylote toniota, o-j2—o-jj"""; microsclera curious asteroid chela; 0-028— o-ojj""". 



This species grows incrusting on a Brachiopod-shell together with some other incrusting 

 sponges; it has a greatest extent of 20 mm and a thickness of about 0-5 ram . The colour (in spirit) is 

 greyish brown. The surface is for the greatest part densely hispid from projecting dermal spicules, 

 but in one end it is smooth, and here there are a couple of conical projections, forming oscular cones. 

 As I have only one specimen, I cannot say, whether it is characteristic for the species that the 

 oscular cones are thus restricted to a special part of the surface. The dermal membrane is thin and 

 not separable; it is densely charged with the curious chelce. 



The skeleton. The dermal skeleton; as said the microscleres form a dense layer in the dermal 

 membrane; the dermal spicules form fibres and bundles stretching in various ways from the main 

 skeleton or quite from the base up to the dermal membrane; the direction of the fibres is generally 

 almost horizontal, and they reach therefore some length; they are also rather strong, of an average 

 thickness of 0-042 mm ; they terminate in the dermal membrane. The membrane is pierced by spicules 

 which seem to be more or less scattered or forming penicillately spread bundles. As far as I could 

 observe these projecting spicules rise from the underlying fibres, probably from the ends of these; 

 they seem to be wanting or are at all events few in number on the smooth part of the surface, 

 where the oscular cones are found. The fibres formed of the dermal spicules run into the oscular 

 cones, forming in the wall of the cone a dense skeleton of parallel spicules with the ends towards the 

 summit of the cone; above this skeleton the layer of microscleres lies. Quite down at the base of the 

 sponge there is found a number of dermal spicules lying singly and horizontally and thus not taking 

 part in the formation of the fibres. The main skeleton is constructed in the ordinary way and consists 

 of vertical acanthostyli with their heads based on the substratum; the skeleton is not dense, the styli 

 being somewhat scattered. At the base a scarcely perceptible amount of spongin is found. 



Spicula: a. Megasclera. 1. The skeletal spicules are acanthostyli; they are straight or slightly 

 curved, the basal end is the thickest part, but there is no real head-swelling or only a slight one. 

 The styli are spined in the whole length, the spines are of small or medium size and reclined; on the 

 head-end they are larger and straightly radiating. The length is 013 — 0-34 mm , and the diameter at 

 the base is 0-014 — o-02i mm . The styli cannot be said to be divided into two groups but the middle sizes 

 are however rare. 2. The dermal spicules are tornota, they are straight or slightly curved and 

 somewhat fusiform, and they are more or less polytylote. The length is 0-32 — 0-43 mm and the diameter 

 in the middle o-oo6— 0-007"™. b. Microsclera; these are bodies of a very curious shape, I may term 

 them asteroid chelae. Roughly speaking they present a cylindrical shaft which at each end divides 

 into three branches, each bearing at the end four compressed, two-pointed teeth, placed in a square; 

 the shaft is more or less curved. On closer examination it becomes evident that this curious body is 

 a chela. It is as a rule possible to trace the shaft or main axis (PI. IX, Fig. 9 c), and one of the three 

 branches at each end is the direct continuation of the axis; this axis answers to the shaft and the 

 teeth in an ordinary chela; the two other branches at each end, which are generally a little tnmner 

 than the axis, answer to the alse; they issue from the hinder side of the shaft; but the ends of the 

 shaft itself and of the alar branches are all developed in the same way, splitting into four compressed, 









