328 HYALONEMA (OONEMA) HENSHAWI. 



pletely torn off. The cup is 123 mm. long and above, at the margin, 8U 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, whicli 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 amphidiscs, macram- 

 phidiscs 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 n- 

 600 )u long, most frequently about 390 m, and 10-22 fi 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 ^ long, farther up. The 

 maximum thickness of the distal ray, together with the spines, is 15-68 m; in 

 those rays over 500 n long this thickness is always over 40 ix. The lateral rays 

 are 37 ju-70 /i long; in the dermal pinules with a distal ray over 500 fi in length 

 the lateral rays are always over 50 ^ 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 fj. 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 M long have been observed, while the distal ray of the latter is only quite 

 exceptionally less than 320 /x 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 /x long, generally 342-650 fi, and at the base 12-27 /i 

 thick; in those over 600 /x long, always 20 fj. 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 n; in those over 600 fi in length 

 this thickness is always over 64 ix and usually about 80 /x. The lateral rays 



