HYALONEMA (HYALONEMA) OBTUSUM. 153 



Hyalonema (Hyalonema) obtusum, sp. nov. 

 gracilis, var. nov. 



Plate 33, figs. 1-24; Plate 3-t, figs. 1-19; Plate 35, figs. 1-37; Plate 36, figs. 1-45; Plate 37, figs. 1-22; 



Plate 38, figs. 1-8; Plate 39, figs. 1-10. 



robusta, var. nov. 

 Plate 39, figs. 11-41; Plate 40, figs. 1-22. 



Two specimens were trawled at two stations in the Tropical Pacific : — 

 Hyalonema (H.) obiusum var. robusta at Station 3681 (A. A. 2) on 27 August, 1899; 

 28° 23' N., 126° 57' W. ; depth 4330 m. (2368 f .) ; it grew on light brown volcanic 

 ooze; the bottom-temperature was 34.6°. H. (H.) o. var. gracilis at Station 3684 

 (A. A. 17) on 10 September, 1899; 0.50' N., 137° 54' W. ; depth 4504 m. (2463 f.) ; 

 it grew on light yellow-gray Globigerina ooze. These sponges are distinguished 

 from their nearest allies by the stout truncate or terminally rounded spines on 

 their macramphidisc-shafts. To these the name refers. 



Although on the whole very similar in their spiculation, these two sponges 

 differ in respect to their external appearance and certain characters of their 

 skeletal element so that I consider them distinct varieties. The spicules of the 

 specimen from Station 3681 (A. A. 2) are generally speaking stouter, those from 

 Station 3684 more slender. I therefore name the former H. (H.) o. var. robusta, 

 and the latter H. (H.) o. var. gracilis. 



Shape and size. The specimen of var. robusta is rather fragmentary, its super- 

 ficial parts having to a great extent been lost. It consists (Plate 39, fig. 33) of a 

 flattened body, 65 mm. long, 12 mm. thick, and 42 mm. broad above. Below 

 it becomes narrower, and there protrudes from its rounded lower end a bundle 

 of stalk-spicules. This bundle, where it arises from the sponge-body, is about 

 2.6 mm. thick. The stalk-spicules forming it are broken off at a distance of 

 35 mm. from the lower end of the sponge. 



The specimen of var. gracilis is well-preserved, but destitute of the stalk ; the 

 sponge-body having apparently been pulled off the stalk-spicules by the trawl. 

 It has the shape of a short and broad spindle or top (Plate 33, fig. 15), is 47 mm. 

 long (high), and has a maximum transverse diameter of 30 mm. The lower end, 

 from which in life the large stalk-spicules arose, is now simply rounded off. 

 The upper end consists of a gastral cone closely enveloped by the thin, frill-like 

 margin of the wall surrounding the gastral cavity. The cone (Plate 33, fig. 16a) 

 is 9 mm. high, nearly cylindrical, circular in transverse section, terminally 

 rounded, 6 mm. thick at the base, and 4 mm. at the end. Its end is sUghtly 



