PLATE XV. 



All the figures in this Plate illustrate the structure of Tinoporus. 



Fig. 



1. — External view of a couical specimen of Tino- 

 porus vesicularis ; magnified 23 diameters. 



2. — Portion of a section of the same, parallel to the 

 base, showing an irregularly concentric ar- 

 rangement of chambers, the floors of which are 

 perforated with numerous foramina; magnified 

 50 diameters. 



3. — Section of the same in the direction of the axis 

 of the cone, showang at a the spherical pri- 

 mordial chamber, and at b and c the chambers 

 first connected with it on either side ; show- 

 ing also the manner in which the succes- 

 sively-formed chambers are piled one upon 

 another vertically, with the large lateral 

 orifices of communication between adjacent 

 chambers ; magnified 50 diameters. 



4. — Ideal representation of a portion of the same, to 

 show the relations of the chambers, which are 

 divided from each other horizontally by cribri- 

 form floors, and laterally by solid walls, in 

 ■which there are large apertures, a, a, a, open- 

 ing into adjacent chambers. 



5. — Australian variety of Tinoporus baculatus, en- 

 larged 50 diameters, to show the areolated 

 character of the surface of the disc, with 

 elevated tubercles disposed between the 



Fig. 



areolse, and the furrowed surface of the ra- 

 diating prolongations. 



6, 7 . — Other specimens of the same variety, showing 

 marked difierences in conformation ; magnified 

 20 diameters. 



8, 9. — Specimens of the Philippine variety of the 

 same ; magnified 12 diameters. 



10. — Portion of a section of the Philippine variety, 

 showing at a the canal-system interposed be- 

 tween the chambers, and at b its reticular 

 distribution in the solid commencement of one 

 of the radiating outgrowths. 



11. — Section of the basal portion of one of the radiating 

 outgrowths of T. baculatus, showing the man- 

 ner in which the chambers are clustered round 

 the axis, and in which the axis is traversed by 

 canals radiating from its centre to its circum- 

 ference. 



12. — Section of the central portion of T. baculatus 

 passing through the median plane, showing at 

 a, a, its regularly spiral commencement (not 

 distinguishable from that of a Calcarina), the 

 origin of the spines from the intermediate 

 skeleton of the spire, aud the early exchange of 

 the spiral type for an irregular clustering of the 

 chambers, as seen at b ; magnified 80 diameters. 



