14 



F. ARNESEN. 



[REP. OF THE -.MICHAEL SARS" NORTH 



Isops pacfjydermata Sollas. 



PI. IV fig. 3 



Vide litter: 15, p. 98. 



St. 23. One specimen. 



An irregular rounded mass about 3 cm. long and 

 2 cm. broad attached together with a small Sidonops sp? 

 to a piece of coral and nearly entirely enveloping it. 

 The uniporal pores and oscula open with chones at the 

 summit of small tubercles. Colour in spirit cream white. 

 Cortex about 1 mm. thick. 



This form, if not a typical Isops pachydermata Sollas, 

 seems at least to be a variety of this species. As will 

 be seen, the measurements of the spicula agree tolerably 

 well with those in Isops pachydermata Sollas but for the 

 subcortical spherasters, which are about double the size 

 and for the presence of the dichotriaenes, sparsely obser- 



ved — if they really belong to the sponge and not to the 

 foreign bodies, abundantly present. 



The spicules are: Megasclera: Oxea, fusiform, 

 usually curved, not sharply pointed, about 2.50 mm. long- 

 by 0.06 mm.; orthotriaene, rhabdome conical, 1.2 — 1.7 mm. 

 long by 0.044 immediately below the ramification, cladi 

 0.680 mm. long by 0.037 at their origin; dichotriaene, 

 rhabdome 0.595 mm. long, protoclad 0.206 mm. long 

 and deuteroclad 0.255 mm. long. Microsclera: sterraster, 

 ellipsoid, 0.250—0.390 mm. by recpectively 0.187- -0.272 

 mm.: small spheraster with a large centrum, total diameter 

 0.018 mm.; subcortical oxeote spheraster, total diameter 

 0.067 mm., centrum well developed, the length of single 

 actine 0.025 mm.; oxyaster with 2 — 8 actines, the length 

 of a single actine in the triod form about 0.060 mm. 



St. 



Geographical distribution: Isops pachydermata Sollas has been recorded from: 



Locality 



Depth 

 m. 



Tempera- | Nr. of 



ture specimens 



Expedition or authority 

 Litterature 



56 32" 9' N., 65" 0' W. (Bermuda) 



234 39° 2' N., 30° 15' W 



242 , 38° 9' N., 30° 19' W. (Azores) 



23 35" 32' N., 7" T W. Spanish Bay. 



1966 Coral mud 



454 ferruginous 

 gravel 



861 Sand, cinders 



1215 , yellow mud 



10° 



? "Challenger" 



Sollas: Tetractinellida, p. 236, 

 One very fine i Topsent: Spongia Atl. Nord in Res. 

 specimen Camp. Sci. Monaco fasc. II. 1892, 



p. 49. 

 Two small 



One 



"Michael Sars" 



Sidonops sp.? 



PI. IV fig. 5. 



St. 23. One specimen. 



St. 24. Two specimens. 



All the specimen are spheroidal, that from station 

 23, attached together with Isops pachydermata to a piece 

 of coral, having a diameter of about 2.5 cm. and those 

 from station 24, both free, having respectively a diameter 

 of 6 cm. and 7 cm. They are much abraded, but seem all 

 to have been densely hispid. Colour in spirit yellowish 

 brown. The specimen from station 23 is provided with 

 one praeosculum, 2 mm. in diameter. Of the specimens 

 from station 24 only the larger one has a praeosculum 

 (diameter 7 mm.). I have not been able to identify 

 any of the specimens with any known species. On the 

 other hand 1 do not consider the material in hand suffi- 

 cient for erecting a new species. 



The spiculation of the specimen from station 23 

 resembles much that of Sidonops baretti, but for the 

 absence of the anatriaenes and protriaenes, which have 

 not been observed, and for the presence of orthotriaenes. 



The spicules here observed are: Megasclera: Large 

 amphioxea, 4 — 5 mm. long by 0.170 mm.; small oxea 

 0.370 mm. long; dichotriaenes, the rhabdome of which 

 is 4.10 mm. long by 0.170 mm., the protoclad 0.170 mm. 

 and the deuteroclad 0.340 mm.; orthotriaenes, rhabdome 

 5.1 mm. by 0.170 mm. and cladi 0.510 mm. Micros- 

 clera: sterraster, 0.296 — 0.370 mm. in diameter; spined 

 oxyaster 0.050 mm. in diameter; spheraster 0.011 mm. 



The spiculation of the specimen with praeosculum 

 from station 24 includes: Megasclera: large amphioxea 

 0.510—0.680 mm. long by 0.085 mm.; small oxea 0.320 

 mm. long; dichotriaenes, rhabdome 8.5 mm. by 0.170— 

 0.250 mm., protoclad 0.425 mm. long and deuteroclad 

 0.680 mm. long; anatriaenes, rhabdome about 23 mm. 

 long, cladi 0.170 — 0.200 mm. long; protriaenes, rhabdome 

 18.7 mm. long; cladi 0.340—0.530 mm. long by 0.068. 

 Microsclera: sterraster, 0.102 — 0.153 mm. in diamer; 

 spined oxyasters, 0.1295 mm. in diameter; spheraster 

 0.007 mm. in diameter. 



The spicules of the other specimen from station 24 

 are of similar dimensions. 



