73 



minute examination, to belong to this species. We may. characterise our species in the fol- 

 lowing manner. 



Hyalonema longissirnuin. M. Sars. 



Forma gracillima et elongata, capite clavato, supine plerumque oblique truncato, 

 osculo singulo, magno, tubiformi, longe porrecto, marginal! instructo, ubique pluma deusa 

 spiculorum induto ; stirpe longissima et tenuissima, 6 ies 8 ics capite longiore, basin versus sen- 

 sim latiore, radice plus minusve dilatata et curvata fibrillas numerosas flexuosas et arbores- 

 centes emittente. Spicula stirpis vix spiraliter disposita in capitis interiore divergentia fasci- 

 culum formantia magnum et latum, de quo fasciculi tenues spiculorum similium sed minoruin 

 parenchyma capitis sustendentes radiant. Osculum cum cavo magno interno communicat. 

 Color fusco-cinereus, Longitudo maximorum 75 Mm. 



Habitat non infrequens ad insulas Lofotenses in prof. 120 300 orgyar, radice in ar- 

 gillo immersa. 



What therefore distinguishes our species from the. very nearly related H. boreale Lov. 

 is: the far slighter and thinner form; the very unequal proportion between the head and 

 the stem; the situation and shape of the out-flow aperture (osculum) the proportionally longer 

 spicula projecting from the exterior skin, and the arrangement of the axial part penetrating 

 into the interior of the head, which does not run conically, but spreads out fan-like into a 

 wide and thick fascicle of spicula. 



The characteristic form for the Hyalonema: a club-shaped enlarged part, borne at the 

 extremity of a long and thin stalk or stem, the other end of which is sunk in the ooze, and 

 there attached by means of numerous root-fibres, is certainly something quite unusual in this 

 class, but does not appear to be exclusively confined to the genus Hyalonema. On the 

 journey which my Father and I undertook together in the summer 1869 to examine the Fauna 

 of the Hardangerfjord, iny Father discovered in the ooze brought up by the dredge from a 

 great depth (150 300 fathoms) a number of specimens of a minute sponge, which had a 

 very similar habit to that of the H. longissimum already previously found by me at Lofoten, 

 but in certain points exhibited a constant dissimilarity; for which reason also my Father 

 noted it preliminarily as a new species of Hyalonema under the appellation H. parvum. The 

 closer examination to which I have subsequently subjected this supposed Hyalonema has how- 

 ever shown that it belongs to an entirely different generic type; the spicula being formed 

 according to quite a different type; as also the interior structure of the head seems to be 

 very different. The spicula in the head are proportionally of quite an enormous size, and 

 mostly belong to the form of connecting spicula which are named by Bowerbank ,,furcated 

 attenuato-patento-ternate"; among these are found in the exterior skin extremely small star- 

 shaped siliceous deposits. The Spicula in the stem are not, as in the Hyalonema, fusiform 

 with a medial enlargement, but simply needle-shaped. 



