390 HYALONEMA (THALLONEMA) GEMINATUM. 



THALLONEMA, subgen. nov. 



Species of Hyalonema of which the amphidiscs of one kind (the largest) have 

 anchors which appear as if they were double, because some or most of their 

 teeth bear from one to three simple branches. 



The collection contains one fragment of this subgenus. This belongs to a 

 new species. 



Hyalonema (Thallonema) geniinatum, sp. nov. 

 Plate 103, figs. 37-62; Plate 104, figs. 1-14; Plate 105, figs. 1-14. 



There is in the collection one small fragment of this species. It was trawled 

 in the Central Tropical Pacific at Station 4740 on 11 February, 1905; 9° 2.1' S., 

 123° 20.1' W.; depth 4429 m. (2422 f.); it grew on a bottom of dark gray 

 Globigerina ooze; the bottom-temperature was 34.2°. 



Many of the anchor-teeth of the largest amphidiscs are provided with 

 from one to three branches, which makes the anchors of these spicules appear 

 doubled. To this the name refers. 



Shape and size. The fragment is an oval lamella, 50 mm. long, 34 mm. 

 broad, and has a maximum thickness of 3 mm. 



The colour in spirit is light dirty brown. 



The skeleton. A dense fur, composed of the distal rays of superficial pinules, 

 covers the intact parts of both faces of the lamella. Much smaller, probably 

 canalar pinules are found in the interior. Besides the lateral rays of the super- 

 ficial pinules the lateral rays of pentactine megascleres and paratangentially 

 extending amphioxes are found in the superficial membrane. Amphioxes similar 

 to the superficial ones, hexactine megascleres, and microhexactines occur in 

 large numbers in the choanosome. The sponge possesses four kinds of amphi- 

 discs: — large geminate macramphidiscs, ordinary large macramphidiscs, small 

 macramphidiscs, and micramphidiscs. All these kinds of amphidiscs are 

 abundant. 



Superficial pinules are, as above ^tated, found on both sides of the lamella. 

 Those on the one side are very similar to those on the other. The only difference 

 between them which I could detect is that the basal thickness of the distal ray 

 appears to be in those of the one face (the dermal ?) on the whole slightly greater 

 than in those on the other (the gastral ?) . 



The dermal and gastral superficial pinules (Plate 103, figs. 58-62) are pentac- 



