\ir\i:r.\ 



I 'MMKineflt sfoe is 90/u long x 4/u to SM thick. In some npocuncns 



tin- maximum size is 90 M long. 



Am. ii- the unliiiary oxea there are a very few r type oxea. It is uncertain 

 whether these are always present It seems probable that in those 

 .ijMviim ii- in which the oxca arc very scarce there may lie none of P type. 



(/) Rcfringent oxea, similar to the smaller and thinner sizes of (a) and usually 



nearly straight 



'l'h Trir<t<liates ate of one sort : 







(r) Alate triradiates, with the basal ray longer than the paired rays. Basal ray 

 straight, tapering, fairly sharply pointed, 90 M to 140 M long x 5/ to 10 M 

 thick. Paired rays equal, bent very slightly downwards, tapering slightly 

 for about two-thirds of their length, then fairly sharply pointed, 50 M to 

 90 M long x 5ft to 7 A* thick ; oral angle 130 to 140. 



The Qtuidriniiliate* are of one sort : 



(</) Alate quadriradiates, facial rays the same as the triradiates (c). Apical 

 ray sharply pointed. 



Oscular spicules : 



(*) Oxea from the fringe, like (a) but shorter, with bluntly pointed lance heads, 



55 M to 65 M long x 5 M to 6 M thick. 

 (/) Quadriradiates from the oscular e<lg c like (/), but of the smallest size, the 



paired rays rather more bent Oral angle 160. 



GRADE HETEROCOELA POL. 



FAMILY 8YCETTIDAE DKNDY. 



TENTHRKNODW. 



A Sycettid in which the radial chambers, with freely projecting distal cones, are 

 " linked " so as to form a reticulated pattern round the large inter-canals. 



This genus contains two species. In both these species the sponge is in the form 

 of a tube, usually more or less bent, the cross-section being probably circular when 

 alive, though it is considerably flattened in some of the preserved specimens. The 

 diameter of the tube is greatest near the middle of its length. It tapers to the base, 

 which is rounded off, and also to the top, which terminates in the oscule. The interior 

 of the tube forms the gastral cavity. The inner or gastral layer is supported by a 

 special skeleton of tri- and quadriradiates, the apical rays projecting into ^thc gastral 

 cavity. Outside the gastral layer stand the flagellated chambers, pointing more or 



2 I 2 



