ItEPORT ON THE HEXACTINELLIDA. 



407 



Key for the Determination of Genera and Species. 



This Table includes those living Hexactincllida in wliich the structure is sufficiently 

 well known to admit of accurate characterisation. 



PAGE AND PLATE 



A. Witli ampliidises and without hexasters, 



B. Witliout aniphidiscs and with hexasters, 



I. Ampiiidiscophoiia, including the single family Hyalonematidae. 



Cup-shaped (exceptionally plate- or ear-shaped) body 

 ■with a simple round sharply contoured terminal 

 oscular region, ..... 



Elongated club-shaped body with internal anastomosing 

 tubular network and narrow lateral oscular zones, . 



II. Hyalonematin.e. 



A slender, long, very sharply defined basal tuft of spicules 



with four-toothed anchor spicules {Hyalonema, Gray), 

 A broad, short, less sharply separated basal tuft of spicules 



with bidentatc anchor spicules, 

 III. Hijalonema. 



The rays of the small parenchymal oxyhexacts are 



altogether .straight, .... 



Some of the small parenchymal oxyhexacts have straight 



rays, while others are distinctly curved. 

 The rays of the small parenchymal oxyhexacts are 



altogether curved, ..... 

 1 The outer ends of the rays of the small parenchymal 



oxyhexacts bear outwardly bent lateral spines, 

 The rays of the small parenchymal oxyhexacts have no 



curved lateral spines, and are either perfectly smooth 



or slightly rough, ..... 

 "2 Sponge-body of a perfectly conical form with oscular 



sieve-plate on the broad upper end. The small 



parenchymal oxyhexacts are rough. 

 Sponge not exactly conical but more or less swollen out. 



The parenchymal oxyhexacts are smooth, . 



3 The terminal umbels of the larger amphidiscs have 



slender, pointed marginal rays. 



The terminal umbels of the larger amphidiscs hear broad, 

 shovel-shaped, marginal rays, 



4 The dermal pinuli have short, somewhat closely appressed 



lateral sjjines on the projecting ray, which is always 

 slender and usually ends in a long drawn out point. 



The dermal pinuli have a broad, superiorly truncate, 



' radial ray with long distant lateral spines. Tliere 



is no oscular sieve-plate, .... 



L 

 VII. 



II. 



SempereUa schultzei, 



III. 

 IV. 



1 



6 



12 



Hyalonema eebuense, 



. 261 



LI., LII. 



228 



