1 88 PORIFERA. II. 



other end; in the very finest developmental forms one end is pointed, b. Microsclera ; these are of two 

 forms, isancorse unguiferse and birotulse. i. The ancorse are constructed quite as those of the pre- 

 ceding species, but they have from nine to thirteen free teeth at either end. Also here one or two 

 teeth are found which are connected behind with the shaft; sometimes these teeth coalesce so 

 completely with the shaft, that they are almost not to be traced, and otherwise there is the same 

 irregularity as in the preceding species. In a few cases the shaft is attached in the middle, and the 

 teeth are free all round, but the shaft is also then curved. The length of the ancora is 0-048— cro65'" m , 

 in a few cases up to o-074 m,n , the thickness of the shaft is 0-004— o-oo58 mm . Some developmental forms 

 were seen, showing only a slight swelling at either end, even when the shaft has reached a rather 

 considerable thickness; later slight ribs are formed, which develop into the teeth. 2. Birotulse are 

 of the same structure as in the preceding species, but they have more teeth, from thirteen to ca. twenty; 

 how great the number may be, I cannot decide, as I have not been able to count them with certainty. 

 The length is 0-015 — 0-020""", the breadth across the circle of teeth ca. o-oo5 mm , and the thickness of 

 the shaft o , ooio ,nm . The microscleres are found throughout the sponge and especially in the dermal 

 membrane, in which the ancorse seem more particularly to occur; the birotulse, otherwise, are present 

 in far greater numbers than the ancorse. 



This species is peculiar by the fact that its skeletal spicules are oxea; another lotroc/iota-species, 

 I. birotidata Higgin, is stated to have diactiual skeletal spicules, which are not, however, oxea, but 

 strongyla; and the fact seems to be that these spicules are really styli with rounded points. In the 

 present species, on the other hand, the question is of real oxea with quite equal ends, neither show 

 their developmental forms any trace of a monactinal origin. 



Locality: We have a rather copious material of the species, but most specimens are damaged. 

 Station 9, 64 18' Lat. N., 27 00' Long. W., depth 295 fathoms; station 10, 64 24' Lat. N., 28° 50' Long. W., 

 depth 788 fathoms; station 89, 64 45' Lat. N., 27 20' Long. W., depth 310 fathoms; station 94, 64° 56' 

 Lat. N., 36 19' Long. W. , depth 204 fathoms; station 97, 65 28' Lat. N., 27 39' Long. W., depth 450 

 fathoms; station 98, 65 38' Lat. N., 26 27' Long. W., depth 138 fathoms; further it has been taken at 

 62 29' Lat. N., 50 17' Long. W., depth 160 fathoms, 6i° 10' Lat. N., 5 46' Long. W., depth 160 fathoms 

 (Ad. Jensen, the cruise of the Michael Sars» 1902). The localities are situated in the Denmark Strait 

 and east of the Faroe Islands. The depths are 138—788 fathoms. 



3. I. abyssi Cart. 

 PI. XVIII, Fig. 3 a-d. 



1874. Halichondria abyssi Carter, Ann. Mag. Nat. Hist., Ser. 4, XIV, 245, PI. XIV, figs. 26—28, PL XV, 

 fig. 40 a— c. 



We have not this species in the Ingolf-material, but I have examined a preparation of 

 Carter's type specimen kindly sent me by Dr. Kirckpatrick. Carter's description of the spicu- 

 lation is chiefly correct. The megasclera are oxea and styli, and the dermal spicules are tylota. The 

 oxea are curved, almost always with a rather sharp bend in the middle, sometimes irregularly; the 

 points are rather long. The oxea have a length of o-6— o-6y mm and a thickness of 0010— o-oi4 mm . The 



