294 



pattern. The shallow gastral cavity is 3 mm deep, and has several large 

 exhalant openings in its floor. 



The skeleton. — The skeleton of the dermatosom is mainly con- 

 structed of square meshes formed by the tangential rays of hypodermal 

 pentactins, of pinules and amphidisks; that of the gastrosom, of diactins 

 with a central swelling, and arranged in longitudinal and transverse 

 strands forming an obscurely square meshed reticulum; no autogastral 

 pinules occur; the choanosom is supported by a cubical-meshed frame- 

 work. 



The spicules. — Parenchymal regular hexactins with smooth sharp 

 pointed rays, straight or slightly curved, 300 X 15 /t in length and 

 basal thickness respectively. 



Parenchymal diactins (rare) 450X8 ii, with central swelling. 



Marginalia 938 // long, 11 // thick in centre, with four central 

 knobs; with proximal end smooth, distal end with spines similar to 

 those of the pinuli, but larger. 



Basalia, monactinal or with denticulate spiral ridge; with pronged 

 anchor at the lower end. 



Auto-dermal pentactin pinuli with slender, rather finely spined, 

 distal ray 480 /< long, with fine hair-like end. Pentactin hypodermalia, 

 with smooth, sharp-pointed rays, the tangentials being 550X24/«. 

 Stauractin acanthophores with rays 100 ii long, smooth in central part, 

 spined at distal ends. 



Autogastral diactins, 1070 X It) //, curved, and with central swelling. 



Macramphidisks, unusually small, varying from 95 — 111 /t in length ; 

 with hemispherical — not bell-shaped — umbrellas 18,5 n in diameter, 

 and with 8 shovel shaped rays 30 u long, 10 u broad, with lancet-shaped 

 pointed ends. 



Mesamphidisks of two kinds, (a) 60 ii long; with hemispherical 

 umbrellas 18,5 ii long, 21,4/« broad, with 12 teeth like those of the 

 macramphidisks, but relatively narrower; (b) 57 n long; with bell-shaped 

 umbrellas 25,7 u long, 21,4 ii broad, with 12 sharp-pointed ligulate rays. 



Micramphidisks from 8,5 — 23 ii in length. Micro-oxyhexactins 

 with smooth rays 52 u long, and with a deep curve at junction of middle 

 and outer third. 



Thanks to the diagnostic tables of species of HiiaJonevta drawn up 

 by F. E. Schulze, (Valdivia, Hexactinellida 1904. p. 161, 163) it is 

 possible to distinguish with ease the new form from the 45 already 

 known species. Hiialonema drygakkii belongs to the group of five species 

 in which the umbrellas of the macramphidisks have shovel-shaped lancet- 

 pointed ends, and the micro-oxyhexactins have strongly curved rays. 

 In H. apertwit F. E. Sch. the rays of the oxyhexactins are rough. H. 



