328 HYALONEMA (OONEMA) HENSHAWI. 
pletely torn off. The cup is 123 mm. long and above, at the margin, 80 mm. in 
transverse diameter. The wall of the cup is only 6 mm. thick. A great part 
of the dermal membrane is lost; of the gastral membrane extensive tracts are 
present. The lower part of the gastral membrane, which lines the deeper 
parts of the cavity of the cup, appears to contain but few efferent pores. Exten- 
sive pore-sieve nets, with pores sometimes 1.7 mm. in diameter (Plate 97, fig. 
32), occur in its upper part. 
The colour in spirit is rather dark dirty brown. 
The skeleton consists of dermal, gastral, and canalar pinules; hypodermal 
and hypogastral pentactines; superficial paratangential and choanosomal 
more or less radial amphioxes; choanosomal hexactine megascleres; abundant 
microhexactines in all parts of the body; and three kinds of amphidises, macram- 
phidises and large and small micramphidiscs. 
The dermal pinules (Plate 97, figs. 2, 31) are nearly always pentactine, hex- 
actine forms being met only exceptionally. The distal ray is straight, 180 u— 
600 » long, most frequently about 390 yu, and 10-22 » thick at the base. It ends 
in a terminal cone and bears spines, which are short, conical, and vertical on its 
basal part, but strongly inclined and large, sometimes 25 u long, fartherup. The 
maximum thickness of the distal ray, together with the spines, is 15-68 »; in 
those rays over 500 u long this thickness is always over 40 u. The lateral rays 
are 37 »-70 » long; in the dermal pinules with a distal ray over 500 u» in length 
the lateral rays are always over 50 u long. These rays are cylindroconical or 
nearly cylindrical, and rounded at the end. They bear a few scattered spines, 
which usually congregate a little beyond the middle of the length of the ray. 
The proximal ray of the few hexactine forms is 15-75 » long. The dermal pinules 
of the lower part of the body appear to be on the whole shorter than those of 
the upper part. Among the former a fair number with distal rays only 260- 
280 » long have been observed, while the distal ray of the latter is only quite 
exceptionally less than 320 u long. 
The gastral pinules (Plate 97, figs. 1, 3-5, 29, 30) are similar to the dermal, 
and like them nearly always pentactine, exceptionally hexactine. Their distal 
ray is straight, 142-710 u long, generally 342-650 », and at the base 12-27 u 
thick; in those over 600 » long, always 20 u or more thick. The spines on the 
distal ray of these gastral pinules appear to be stouter, shorter, and less inclined 
than those on the distal ray of the dermal. The maximum thickness of the 
distal ray, together with the spines, is 25-85 »; in those over 600 u in length 
this thickness is always over 64 » and usually about 80.4. The lateral rays 
