HYALONEMA (HYALONEMA) TYLOSTYLUM. 229 



unifornily curved in the same direction for the remainder of their length. The 

 tips of the teeth are sometimes abruptly bent inward. Occasionally in their 

 middle-part, particularly in the forms with curved shaft, the teeth are slightly 

 cur\'ed outward. 



The micramphidiscs (Plate 67, figs. 16-21; Plate 68, figs. 5, 6) are in speci- 

 men (a) 24-34 M long, in (6) 20-32 fi. The shaft is straight, cylindrical, and 0.8- 

 1 fj. thick. It bears a small number of irregularly scattered spines in its usually 

 gradually thickened central part. The terminal anchors are in specimen (a) 

 5-8 M long, a quarter to a third of the whole spicule, and 5-9 m broad; in (6) 

 7-10 IX long and 6.2-10 /x broad. The proportion of anchor-length to anchor- 

 breadth is 100 : 87 to 130, on an average 100 : 99.1. 



The nearest allies of these sponges are Hyalonema {Hyalonema) placuna and 

 H. (H.) tyhstylum. From H. (H.) placuna they differ: — by their external shape; 

 by possessing abundant minute slender centrotyle amphioxes ; by having dermal 

 pinules with much longer lateral and somewhat longer distal rays; by the distal 

 rays of their gastral pinules being shorter; by their amphidiscs having smaller 

 anchors; by theu' microhexactines being much less spinj^; and by other char- 

 acters. From H. (H.) tylostylutn they differ by the larger size of their pinules; 

 by the possession of numerous minute, slender amphioxes and microhexactines 

 with four reduced rays; by the absence of tylostyles; and by having consider- 

 ably smaller macramphidiscs. 



Hyalonema (Hyalonema) tylostylum, sp. nov. 

 Plate 69, figs. 6-25; Plate 70, figs. 1-10. 



I establish this species for two specimens trawled off northern Peru at 

 Station 4656 on 13 November, 1904; 6° 54.6' S., 83° 34.3' W.; depth 4063 m. 

 (2222 f.); the bottom consisted of fine, green mud mixed with gray ooze; the 

 bottom-temperature was 35.2°. 



Shape and size. Both specimens are compressed, lamellar, and broader at 

 one end than at the other. The narrower end is rounded, the broader irregular 

 and lacerated. A stalk about 2 nam. thick and broken off short arises from the 

 middle of the convexity of the narrower, rounded end. One of the specimens 

 (Plate 70, fig. 6) is 50 mm. long, 33 mm. broad, and 7 nun. in maximum thick- 

 ness; the other measures 75 by 50 by 10 mm. In both specimens the upper part 

 consists of two lamellae pressed together and joined laterally and below. This 

 structm-e and the spiculation of the inner and outer surfaces of the lamellae 



