Genus of Fossil Ilexactinellid Sponges. 2/5 



5, cast of Sfxnuliati; spicule filU'd muru or Iuh.s coniplelely with 

 irou pyrit's ; /, divergiii".' longitu<Hiiiil, uud t, curved nidiatiug 

 fibres." x'M. 



ri.ATK III. 



Fitj. 1. Fibre Hurroiindiiifj^ an oscule, from n .specimen which lin.s beeu 

 etched with iicid, seen by reflected light : », one of the projecting 

 spines, x oO. 



Fiy. 2. Section ulong an e.vcurront canal of the oscular plate, after etching 

 with acid, seen by reflected light : r, fine suj)erfi(ial network 

 rooting over the o.'^cule ; />, fibre produced from it, depending into 

 the canal ; «, email irregular tibres'growing out from the skeletal 

 network. The an-ow indicates the original course of the out- 

 flowing current. x'tO. 



Fi(j. 3. Surface of oscular plate near one of the concealed oscules : 

 .<, coai-jjie skeletal tibre.^, smaller than in the interior of the plate, 

 spined, and ])r^sing under ;•, the secondary rete. XliO. 



t^y. 4. A mesh of the outer .><keleton-fibre, giving off at its margins some 

 of the fine superficial network, x 140. 



Fiy. o. A part of the o.scular plate represented in PI. II. fig. .3, magni- 

 fied to .show : — a, an acerate spicule imbedded in the network ; 

 and h, part of an abnormally fine skeletal network, a band of 

 which traverses the whole of this specimen of the oscular plate. 

 X30. 



Pl.\te IV. 



Fiy. 1. Secondary rete, seen by reflected light : /, fibres parallel with the 



surface ; s, free spinose ends of fibres normal to the surface. 



Xl04. 

 Fiy. 2. Projecting spinose fibres (« of fig. 1), resembling the fir-cones of 



Farrea occa. X 104. 

 Fiy. .3. Similar to tig. 1, but showing a finer meshwork. Xl04. 

 Fiy. 4. Fiue superficial network, seen near the ba^ie of the oscuLir plate 



bv reflected light, where it conceals the spinose fibres of fig. 2. 



Xl04. 

 Fiy. 5. Similar network, but occurring between the spines of fig. 2. The 



sexradiate ai'raugemeut of the fibres is well seen iu this instance. 



Xl04. 

 Fiys. 6 & 7. Minute sexradiate reticulation proceeding from the spinose 



ends of fig. 2. x 104. 



Plate V. 



Fiy. 1. Superficial network from the surface of the posterior mass: m, 

 intermcsh ; /, fibres; ii, secondary intermesh. xCiO. 



Fiy. 2. A part of fig. 1, more highly magnified, showing the compound 

 nature of the fibre. X 190," 



Fiy. 3. Network beneath fig. 1 , consisting of /, large fibres, the meshes 

 between which are webbed with the fine fibrelets, //. X 140. 



Fiy. 4. Fragment of superficial network from anterior face of same spe- 

 cimen, showing clearly a sexradiate arrangement. X 140. 



Fiy. 5. Entirely spined cylindrical spicule, projecting from the face of 

 the oscular plate. X 140. 



