PORIFERA. III. 



97 



The shaft is not cylindrical but somewhat flattened and therefore of different thickness in side and 

 front view, the thickness is in relation to this and to the size of the chela 0-003 an ^ O 4 oo6 mra to O'ooy 

 and o-on mm ; the larger chelae are the most numerous. Sometimes the chelae have the shaft less 

 strongly curved. 2. The sigmata of the larger form are somewhat irregularly curved and they 

 are contorted, always a quarter of a turn or nearly so; their length is rather constant, about 0-021 

 0-028 mm and the thickness about o-ooi mm . 3. The small sigmata quite resemble the sigmata in H. 

 pugio; they are likewise strongly curved, and they are plane; their length is about o-oi4 mm and the 

 thickness scarcely goes beyond 0-0008 mm . The microsclera occur through the whole tissue and the 

 chelae are seen in great numbers in the dermal membrane. 



Locality: Station 15, 66 18' Lat. N., 25 59' Long. W., depth 330 fathoms (bottom temperature 

 -f-o75C.); station 25, 63 30' Lat. N., 54 25' Long. W., depth 582 fathoms, and East of the Faroe 

 Islands, depth 230 fathoms (Ad. Jensen, the cruise of "M. Sars" 1902). The localities are situated in 

 the Davis Strait, the Denmark Strait and East of the Faroe Islands. The species must be an in- 

 habitant of the warm area; it is true that station 15 shows a negative bottom temperature, but this 

 station lies just at the very border between the cold and the warm areas. 



The three species just described must be somewhat nearly related, but besides by other 

 characters they may be distinguished by their sigmata alone; H. pugio has only small, plane, circularly 

 curved sigmata, consan guinea only contorted sigmata and planca two forms, contorted and plane. 



42. H. cultrisigma n. sp. 

 PI. X, Fig. 2. 



Incrusting; surface hispid. Spicula: megasclera; the skeletal spicules acanthostyli with a "very 

 slight or no head, they are divided into two groups, large, only spined below, 0-56 0-80 mm , small, spined 

 in the basal half, 0-21 o-jo"""; the dermal spicules tylota 0-23 0-32"""; microsclera three forms, chela 

 arcuatce 0-026 0-042 mm , sigmata of two forms, large, peculiar, somewhat band-shaped, 0-028 o-ojj""*, 

 small, plane, 0-014 0-020""*. 



This species grows as very thin incrustations on different bottom material as pebbles and 

 shell-fragments and in one case on a Hexactinellid skeleton. The greatest extent it reaches is i6 mm ; 

 it may vary a little in thickness, but it is however always very thin, not reaching 0-5 mm . The colour 

 (in spirit) is whitish. The surface is in the present condition of the sponge very hispid with long 

 projecting spicules. The dermal membrane is a thin film. Oscula and pores were not seen, but some 

 circular canals could be seen through the dermal membrane. 



The skeleton. The dermal skeleton is formed by bundles of dermal spicules stretching from or 

 almost from the base to the surface; the bundles have a more or less oblique direction and are often 

 almost horizontal for a distance; they do not project beyond the surface, and there are no spicules 

 lying in the membrane itself. The bundles are generally weak, consisting of only few spicules. The 

 main skeleton has quite the ordinary construction and consists of acanthostyli with the heads placed 

 on the substratum; the long styli project beyond the surface. At the base there is a small amount 

 of spongin. 



The Ingolf-Expedition. VI. 3. X 3 



