REPORT ON THE HEXACTINELLIDA. 231 



Hyalonema species diversse indefinitai (PI. XXXII. figs. 11-lG; PI. XXXIX. 

 figs. 1-15). 



Of the above-described species of Hyalonema, more or less perfectly preserved 

 specimens were at my disj^osal. so that an approximately accurate investigation was 

 possible, and diagnoses sufficient for the determination of the several species were 

 obtained. But besides the above, the Challensrer collection included several fragments 

 which could be certainly enough referred to the genus Hyalonema, but not with any 

 definiteness to any of the species pre\aously known, or now established by my investiga- 

 tions. They belong to new, not yet described species. Following the frequent precedent 

 of many investigators, I might have selected the most prominent characteristics of these 

 forms, and used them for the erection of distinct species. I have, however, preferred to 

 refrain from designating these imperfect and torn fragments, of which I should be unable 

 to frame a description or diagnosis sufficient for their re-identification. I have, nevertheless, 

 figured several of the more remarkable spicular structures of sponges from these localities 

 for the use of future investigators, and by way of extending our knowledge of the variety 

 of form within the genus Hyalonema. 



Several large but insufficiently preserved fragments, referable to a sponge form 

 about the size of one's fist, were dredged from the Mid-Pacific, near the Equator (Station 

 271, lat. 0° 33' S., long. 151° 34' W., where Hyalonema dejyressum was found), from a 

 depth of 2425 fathoms and a Globigerina ooze ground. The smooth oxyhexacts and 

 oxydiacts of the parenchymal skeleton do not exhibit any marked peculiarities. Small 

 oxyhexacts are only represented by somewhat abundant forms with straight or slightly 

 curved pointed rays (PL XXXII. fig. 15). The complete absence of small curved 

 oxyhexacts essentially distinguishes this form from the species Hyalonema depressum 

 found in the same locality. The hypodermal oxypentacts and oxydiacts of the 

 dermal skeleton resemble, in form and size, the similar forms of Hyalonema clavigerum. 

 The autodermal pentact pinuli are, however, peculiar, and resemble most closely 

 the external pinuli of Hyalonema rohustum. Like the latter, they exhibit short, 

 strongly developed, and minutely spinose basal rays, and also a free, spindle-shaped, 

 somewhat bushy distal, almost 0"4 mm. in length, beset with numerous rather long 

 spines disposed like scales. The very end of the ray frequently exhibits a strongly 

 developed, thick point, which is not very satisfactorily represented on PI. XXXII. fig. 16. 



The much extended, larger and medium-sized amphidiscs of the skin, are distinguished 

 by the slender, delicate character of the slightly toothed axial rod, and also by the long- 

 umbels, which bear eight slender rays, and exhibit a campanulate form, somewhat trun- 

 cated terminally. These forms of amphidisc differ greatly in size, as may be seen from 

 some of the modifications represented in PI. XXXII. figs. 11, 12, 13. Occasional 

 giant-forms (fig. 11), 0'4 mm. or more in length, occur. Besides these, there is an abun- 



