HYALONEMA (PHIALONEMA) BREVANCORA. 
359 
Shape and size. The larger fragment (Plate 55 , fig. 1) is an irregular, porous, 
flattened mass measuring 47 by 38 by 8 mm. The smaller one is only 22 mm. 
long. 
The colour in spirit is dirty white. 
The skeleton consists of pinules; hexactine, pentactine, and rhabd mega- 
scleres; microhexactines; and amphidiscs. In most of the pinules in the 
preparation the distal ray bears relatively very long spines; these pinules are 
probably hypodermal or hypogastral. In some pinules these spines are very 
short; these may be canalar. The hexactine megascleres are found in the 
innermost part of the specimens; the pentactines are no doubt hypodermal or 
hypogastral. The rhabd megascleres for the most part form bundles. The 
microhexactines are numerous, and all of the same kind. Macramphidiscs and 
large and small micramphidiscs can be distinguished among the amphidiscs. 
The small micramphidiscs are abundant, the other amphidisc-forms rare. 
The (probably dermal and gast.ral) pinules with long-spined distal ray 
(Plate 65 , figs. 19-28, 30, 32, 33) are nearly always pentactine, very rarely 
hexactine. The distal ray is straight, 70-89 n long, and 3-4 n thick at the base. 
It bears spines along its whole length. The spines on the proximal third or so 
of its length are very small, straight, and directed obliquely upwards. The 
distal and middle-parts of the ray are covered with spines very unequal in 
length and in curvature, the large and the small ones being here irregularly 
intermingled (Plate 55 , fig. 19). Some of these spines attain a relatively very 
considerable size, the largest being 18-54 n long and about 2 ^ thick at the 
base. The lower spines, both large and small, are usually nearly straight, and 
very divergent (Plate 55 , figs. 22, 25, 28). Farther up the short spines only are 
like this, most of the longer ones being curved, concave to the ray. This curva- 
ture is not infrequently so great that their ends become inclined towards the 
distal part of the ray (Plate 55 , figs. 19, 21, 23). The spines are conic and sharp- 
pointed. Some of the larger ones bear one or two, rarely more, secondary spine- 
lets, usually 2-3 m long, and inclined towards the end of the spines from which 
they arise. The maximum thickness of the distal ray, together with the spines, 
generally is 22-37 /x, rarely as much as 54 fx. The lateral rays are usually 22-37 /x 
long, sometimes longer. They are cylindrical proximally, conic clistally, pointed, 
and beset with numerous oblique spines inclined towards the end of the ray. 
These spines attain a very considerable size, particularly in the distal and 
middle-parts of the ray. The lateral spines of these rays seem to be larger than 
the others; they give to the contour of the ray, when seen from above, a markedly 
