PLATE XXI. 



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



Fig. 

 1- 



G.- 



8. 9 



10.- 



11. 



5. — Interior of the first-formed chambers of five 

 specimens, showing their Globigerine cha- 

 racter and arrangement ; at a, a, are shown 

 the remains of the yellowish-brown spougeous 

 substance by which those chambers were occu- 

 pied : 50 diam. 



-Portion of a group attached to the surface of 

 Poriies (Coral) : 5 diara. 



-Isolated specimen growing on the shell of Pecten, 

 in which the chambers of the last whorl 

 diverge so widely at the base of the cone as 

 to be in great degree separated from each 

 other : 25 diam. 



— External apertures at the apex of the cone of 

 two specimenSj showing their peculiarly Milio- 

 line character : 20 diam. 



-Portion of a specimen partially laid open by grind- 

 ing away the apical portion of the cone ; 

 showing at a the vertical funnel transversely 

 divided, at b its communication with the last 

 chamber, at c its communication with the 

 penultimate chamber ; d, d}, and d^, three of 

 the complete septa dividing the principal 

 chambers ; e, ei, e", secondary septa, partially 

 dividing the principal chambers, but not ex- 

 tending to their central portion; f,f^,f-, in- 

 complete septa projecting inwards from the 

 external wall, but not crossing the cavity of 

 the chamber to reach the opposite wall : 20 

 diam. 



— Section of a very flat specimen, parallel to the 

 base of its cone, but not far from its apex ; 

 a, b, c, d, as in the last figure ; g and ^', por- 

 tions of the canal-system : in some of the 

 chambers are seen spicules resembling those 

 of Sponges : 20 diam. 



— Portion of the external wall, showing the areo- 

 lated aspect it derives from the gentle con- 

 vexities into which it rises between the reti- 

 culations that project on its internal surface ; 



Fig. 



at a is shown the natural external surface on 

 which the foramina are regularly disposed ; at 

 b that surface has been removed by grinding, 

 so as to bring into view the inner layer of the 

 wall, on which the foramina are seen to be 

 deficient along the projecting ribs, but to be 

 more closely set together in the portions sur- 

 rounded by these (see fig. 16) : 30 diam. 

 13. — Portion of a section taken in the same direction 

 as Fig. 11, but represented on a larger scale, 

 showing the annulations of the foramina that 

 are seen obliquely traversing the shell, and the 

 two layers of which not only the principal 

 septa «, a, but also the incomplete septum b, 

 are formed, with the cauals included between 

 them; at c is seen a large dilatation of one 

 of the canals : 75 diam. 

 14. — Portion of the group of Carpenteria growing on 



the surface of Poriies, of the natural size. 

 15. — An unusually large specimen, of the actual size. 

 16.-^Portion of the external wall of a specimen which 

 has been thinned away by the action of acid, 

 showing the reticulated arrangement of the 

 incomplete septa ; the spaces included in the 

 reticulations are in some instances covered in 

 by a thin layer of the shelly wall which has 

 not been removed ; but in most other cases 

 this wall has been eaten away by the acid in 

 the central portion of the reticulation, so as 

 to display the dark, spiculiferous substance 

 ■within : 30 diam. 

 17. — Siliceous spicules (resembling those of Hali- 

 chondria) from the spongeous tissue occupying 

 the chambers of Carpenteria : 75 diam. 

 18. — Section traversing the external wall of one of 

 the chambers perpendicularly to its surface, 

 showing at a, a, the annulated foramina by 

 which it is traversed, and at b, b, b, sections of 

 the imperfect septa on which the foramina do 

 not open : 75 diam. 



