Genus of Fossil UexactinelUd Sponges. 25 



5, cast of sexradiate spicule filled more or less completely with 

 iron pyrites ; I, di^ erging longitudinal, and t, curved radiating 

 fibres. X 30. 



Plate III. 



Fig. 1. Fibre surrounding an oscule, from a specimen which has been 

 etched with acid, seen by reflected light : s, one of the proj ecting 

 spines. X 30. 



Fiy. 2. Section along an excurrent canal of the oscular plate, after etching 

 with acid, seen by reflected light : r, fine superficial network 

 roofing over the oscule ; p, fibre produced from it, depending into 

 the canal ; q, small irregiilai" fibres'growing out from the skeletal 

 network. The aiTow indicates the original course of the out- 

 flowing current. X 30. 



Fi;/. 3. Surface of oscular plate near one of the concealed oscules : 

 s, coarse skeletal fibres, smaller than in the iuterioi* of the plate, 

 spined, and passing under r, the secondary rete. X GO. 



Fi//. 4. A mesh of the outer skeleton-fibre, giving off" at its margins some 

 of the fine supei-ficial network, x 140. 



Fi(/. 5. A part of the oscular plate represented in PI. II. fig. 3, magni- 

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

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

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

 X30. 



Plate IV. 



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



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



Xl04. 

 Fi(/. 2. Projecting spinose fibres (s of fig. 1), resembling the fir-cones of 



Farrea occa. X 104. 

 Fig. 3. Similar to fig. 1, but showing a finer meshwork. Xl04. 

 Fig. 4. Fine superficial network, seen near the base of the oscular plate 



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



Xl04. 

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



sexradiate arrangement of the fibres is well seen in this instance. 



Xl04. 

 Figs, 6 & 7. Minute sexradiate reticulation proceeding from the spinose 



ends of fig. 2. x 104. 



Plate V. 



Fig. 1. Superficial network from the surface of the posterior mass : w?, 

 intermesh ;/, fibres ; «, secondary intermesh. x60. 



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

 nature of the fibre. X 190. 



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

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



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

 cimen, showing clearly a sexradiate arrangement, x 140. 



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

 the oscular plate. X 140. 



