44 



PORIFERA. III. 



but this is not a very safe character, as strongyles more or less polytylote are of frequent occurrence 

 in Hymedesmia; already when he founded the species, Topsent mentioned, that it varies somewhat 

 with regard to the spicules, and in 1904 he again states that this variation takes place to a high 

 degree, the three forms of spicules varying both in size and in shape; according to this I am not at 

 all sure, that all the specimens mentioned by Topsent belong really to the same species. When I 

 have determined my species as Koehleri, my reason is especially the somewhat robust, conical acantho- 

 styli, generally with large, somewhat obtuse or crenulated spines at the head-swelling, the polytylote 

 strongyla with unequal ends and also the shape of the chelse. Now, as already stated, my specimens 

 may also vary to a certain degree, and the acanthostyli are not always so robust, or with so large 

 spines at the base as in the more typical specimens, and the possibility, that there may be more than 

 one, very nearly related species in my material is not quite excluded. 



Locality: Station 9, 64 18' Lat. N., 27 oo' Long. W., depth 295 fathoms; station 16, 65 43' LaL N., 

 26 58' Long. W., depth 250 fathoms; station 54, 63 08' Lat N., 15 40' Long. W., depth 691 fathoms; 

 station 57, 63 37' Lat. N., 13 02' Long. W., depth 350 fathoms; station 98, 65 38' Lat. N., 26 27' Long. W., 

 depth 138 fathoms; further it has been taken East and West of the Faroe Islands in depths of 250 

 and 180 fathoms (Ad. Jensen, the cruise of "M. Sars" 1902). The localities are situated in the Denmark 

 Strait, between Iceland and the Faroe Islands and East of the latter. 



Geogr. distr. Topsent mentions the species from the Bay of Gascogne, depth 648 fathoms, 

 and from the Azores in depths of 318 to 1350 fathoms. At present the species would thus be known 

 from about 66 to 38 Lat N., and between about 2 and 31 Long. W., with a bathymetrical range 

 from 138 to 1350 fathoms. 



2. H. lacera n. sp. 

 PI. V, Fig. 6. 



Incrusting; surface smooth. Spicula: megasclera; the skeletal spicules slender acanthostyli with 

 a slightly marked head, spined only in the lower half part, ovj 0-51""", not divided into two groups; 

 dermal spicules large, generally slightly polytylote strongyla, 0-327 0-47""" ; microsclera chela arcuatce 



Of this species one specimen grows as an irregular incrustation on a worm-tube which is 

 attached to a Hornera lichcnoides, another specimen grows on a mussel-shell; the greatest extent of 

 the specimens is about 15 mm , and the thickness is about 0-5 nim or a little more. The colour (in spirit) 

 is whitish grey or dirty brownish grey, but it is stated to be light dirty green in the fresh state. The 

 surface is smooth, without projecting spicules. The dermal membrane is a somewhat solid film. 



The skeleton. The dermal skeleton is formed of bundles or short fibres, stretching from beneath 

 up to the dermis, upwards they are somewhat penicillately spread; moreover, bundles or somewhat 

 longer fibres are found lying horizontally in the dermal membrane, and finally there are scattered 

 chelae. The main skeleton is constructed in the ordinary way; the styli are very dispersed. So far as 

 I could observe there is some spongin at the base. 



Spicula: a. Megasclera. i. The skeletal spicules are acanthostyli, which are very slender 

 and straight or quite slightly, rarely a little more, curved; the head is generally only very slightly 



