PORIFERA. III. 



24. H. levis n. sp. 

 PI. VIII, Fig. 2. 



hi crusting and very thin; surface finely hispid. Spicula: megasclera; the skeletal spicules 

 acanthostyli with a somezuhat swollen head and small spines, 0-08 0-25""", not divided into two groups; 

 the dermal spicules polytylote tylota or subtylota o-i6o-2i mm ; microsclera small chela arcuata- 



O-O2I O - 



The specimens of this species grow on Brachiopods, shells of Astarte and other mussels and 

 on Placostegus tridentatus. The greatest extent, to which the species reaches, is 19"""; the sponge 

 forms an exceedingly thin incrustation, the thickness is scarcely above O'io nim . The colour (in spirit) 

 is light brownish yellow. The surface is finely and densely hispid from projecting skeletal spicules. 

 The dermal membrane is a thin film. Oscula and pores were not observed. 



The skeleton. The dermal skeleton; the dermal spicules form bundles which go to the surface 

 in an oblique, often very decumbent direction; these bundles are rather scattered. In the membrane 

 the chelse are found sometimes rather numerously, at other times more scattered. The main skeleton 

 consists in the ordinary way of acanthostyli with the head-ends on the substratum; the larger of them 

 project beyond the surface, making this hispid. A small amount of spongin is found at the base. 



Spicula: a. Megasclera. i. The skeletal spicules are acanthostyli which have a somewhat 

 characteristic shape; they are straight or generally somewhat curved; the head-end is somewhat 

 swollen, and they taper into a long apex; as they are rather thick at the head-end and are not 

 especially long, they become slightly club-shaped. The head-end has strong spines, in the small styli 

 the other spines are also rather pronounced, but in the larger ones the spines on the shaft are small, 

 the shaft thus almost being merely gritty; in the longer styli the spines are scattered towards the point, 

 but there is generally no long, smooth apical part. The size varies much, but the styli are not 

 divided into two groups. The length is 0-08 0-25""", the styli thus being rather short; the diameter 

 of the head is about 0-014 0-03""". 2. The dermal spicules are slender, straight tylota or subtylota 

 which are distinctly polytylote; they have a generally rather distinct, longish swelling at each end, the 

 shaft is a little thinner in one end, and the swelling in this end is therefore more marked than in the 

 other. The length is 0-16 o-2i mm , and the diameter about 0-0028 0-004 ram . b. Microsclera; these are 

 chelse arcuatae; they are rather small, the shaft is somewhat strongly curved, the alse are nearly 

 triangular and the tooth elliptical and of the same length as the alse. The length of the chela is 

 0-021 0-024 mm , a d the diameter of the shaft about o-oo28 mm . The chelae seem to be confined to the 

 dermal membrane. 



This species stands very near to baculifcra, but I consider it as distinct; it is especially the slightly 

 spined acanthostyli which distinguish it, and the dermal spicules are also more distinctly polytylote. 



Locality: Station 9, 64 18' Lat. N., 27 oo' Long. W., depth 295 fathoms; station 25, 63 30' Lat. N., 

 54 25' Long. W., depth 582 fathoms; station 85, 63 21' Lat. N., 25 21' Long. W., depth 170 fathoms; 

 station 89, 64 45' Lat. N., 27 20' Long. W., depth 310 fathoms; further it has been taken at 62 29' Lat. N., 

 5 17' Long. W., depth 160 fathoms (Ad. Jensen, the cruise of "M. Sars" 1902). In all seven specimens. 

 The localities are situated in the Davis Strait, the Denmark Strait and East of the Faroe Islands. 



The Ingolf-Expedition. VI. 3. IO 



