PORIFERA. III. 



91 



spines in the whole length, the spines are directed downwards; on the head there are rather long, 

 radiating spines. The length of the large styli is 0-25— 0-31 mm , and the diameter at the base o-02i n,m ; 

 the small styli are o-n— o-i4 ram long with a diameter of the head of o-02i mm . 2. The dermal spicules 

 are tylota which are cylindrical and straight or slightly, irregularly curved; the end-swellings are not 

 large but distinct; the length is 0-26— o-4i7 mm and the diameter in the middle 0-005— 0-008 mm . b. Micro- 

 sclera are of two forms, chelae arcuatae and sigmata. 1. The chelae have an evenly curved shaft, the 

 free middle part of which is a little more than the third part of the length; the alas are lobe-shaped 

 and the tooth elliptical, rounded at the end. The length is 0-034 — 0-038 mra and the diameter of the 

 shaft 0-005 ram . 2 - The sigmata are of ordinary shape, more or less contorted up to a quarter of a 

 turn. The length is 0-028— 0-050 n,m and the thickness between 0-002 and 0-003 mm . The chelae and 

 sigmata seem to be present in about equal numbers; the chelae occur in the wall of the papillae, and 

 for the rest both forms of microscleres seem to occur, so far as I could ascertain, through the 

 whole body. 



This species is distinguished from the preceding in regard to the spicules by the smaller acantho- 

 styli, the tylote dermal spicules and the much smaller sigmata; also the chelae are slightly different. 



Locality: Station 89, the Denmark Strait, 64 45' Lat. N., 27 20' Long. W., depth 310 fathoms. 

 Two specimens. 



37. H. trichoma n. sp. 

 PL III, Fig. 16, PI. IX, Fig. 5. 



Incrusting ; surface smooth, bearing thin papillm. The iter mat membrane with horizontal spicules. 

 Spicula: megasclera ; the skeletal spicules acanthostyli with a small head, spined in the 'whole length, 

 they are divided into two groups, large, 0-20 — 0-24""", small, o-n — o-ij"""; the dermal spicules tylota 

 0-29 — o-j8"""; microsclera two forms, chclce arcuataz 0-034 — 0-042""", plane sigmata 0-058 — o-oj$""". 



Of this species we have only one specimen growing on a shell of an Asfarte; it forms a thin 

 incrustation of a greatest extent of only 6 mm , and it bears one long and thin papilla. The colour (in 

 spirit) is light brownish. The surface is smooth. The dermal membrane is thin and not easily 

 separated. About oscula and pores I can say nothing, as said, only one papilla is present. 



The skeleton. The dermal skeleton; the skeleton formed of the dermal spicules consists of 

 bundles stretching from near the base to the dermal membrane; in the membrane there are horizontal 

 spicules, but they are scattered and not at all dense-lying. The main skeleton is arranged quite in 

 the ordinary way, consisting of erect acanthostyli with their head on the substratum and evenly 

 distributed over it; the largest of them reach to the surface. A small amount of spongin seems to 

 be present. 



Spicula: a. Megasclera. 1. The skeletal spicules are acanthostyli which are straight or 

 nearly so, the head-swelling is small, and they taper slightly towards the point, which is short; they 

 are rather densely spined in the whole length, but the spines are small, only longer at the base; 

 though they do not vary much in length they are yet divided into two distinct groups; the length of 

 the large styli is 020— 0-24 mm , and of the small o-n— o-i3"' m ; the diameter of the head is about o-02i mm , 

 and it is nearly the same in the large and the small styli on account of the basal spines being larger 



