PORIFERA. III. 



47 



Spicula: a. Megasclera. i. The skeletal spicules are straight or very slightly curved 

 acanthostyli; the head is globular, but not however much swollen, the apex is long and evenly 

 tapering; the spines are distinct also in the larger styli; the small styli are entirely spined, in the 

 larger the spines are very dispersed towards the point, but they are most often present out to the 

 point, or only a small part of the apex is smooth; more rarely the styli may be smooth for a longer 

 distance. The length is o-i2— 0-33 mm , and the diameter of the head is 0-012- 0-022 """. 2. The dermal 

 spicules are straight strongyla; they are of the same thickness in the whole length and slightly 

 polytylote; the length is 0-22 — 0-36 mm and the diameter about 0-005 mm . The size of the megascleres 

 may vary a little in various individuals, b. Microsclera; these are chelae arcuatse; they are small 

 and of a particular shape, by which they approach somewhat to the chelse palmatse; the shaft is evenly 

 curved, the tooth is lanceolate, and the alse are connected with the shaft in their whole length, it is 

 therefore chiefly only the curved shaft which distinguishes them from the palmate chelse. The length 

 is 0-028 """ and the diameter of the shaft about 0-002 mm . The chelse occur scattered in the dermal 

 membrane. 



This species is characterised already by its chelse. 



Locality: Station 1, 62 30' Lat. N., 8° 21' Long. W., depth 132 fathoms; station 25, 63° 30' Lat. N., 

 54 25' Long. W., depth 582 fathoms; at Angmagsalik on the East coast of Greenland, depth 140 fathoms 

 (The Amdrup-Expedition 1900); 6i° 40' Lat. N., 7° 40' Long. W., depth 135 fathoms (Ditlevsen); East of 

 the Faroe Islands, depth 250 fathoms (Ad. Jensen, the cruise of "M. Sars" 1902). The localities are 

 situated in the Davis Strait, at East-Greenland and at the Faroe Islands. 



5. H. mollis n. sp. 



PI. VI, Fig. 1. 



Incrnsting ; surface smooth. Spicula: megasclera; the skeletal spicules acanthostyli with a small 

 head, the larger slightly spined and smooth outwards, the smaller spined in the whole length. 0-119— 

 °'52>"""- ""f divided into two groups: the dermal spicules strongyla 0-24 — o-jjj""",- microsclera chela 

 arcuatoe 0-027 — 0-040""". 



Most specimens of this species grow incrusting on Brachiopods, as well on living as on dead 

 specimens, one grows on a shell of a Buceiiium, one on a mussel-shell and finally one on an Oculina. 

 The greatest extent measured is about 20 mm ; the thickness generally does not exceed 0-5""". Two speci- 

 mens grow in a remarkable manner; they are not attached to a definite substratum but grow on sand, 

 gravel and small particles of very different kinds, especially sponge-spicules; they then envelop the 

 substratum, so that the sponge together with the substratum forms irregular, wrinkled masses which 

 seem rather thick, but the real thickness is not greater than given above. The colour (in spirit) is 

 greyish brown. The surface is smooth or nearly so. The dermal membrane is a thin film, but it is 

 for the greater part wanting on the specimens. Oscula ami pores were not to be observed on account 

 of the bad condition of the dermal membrane. 



The skeleton. The dermal skeleton: the skeleton formed of the dermal spicules is strongly 

 developed. Quite down at the base of the sponge the dermal spicules form fibres or fibre-like bands 



