588 DE. CAEPENTEE'S EESEAECHES ON THE FOEAMIMFEEA. 



and showing at a, , #, the csecal diverticula for the retral processes, and at 

 I, b, the meridional canals transversely divided. Magnified 60 diameters. 



Fig. 11. Portion of a section of Polystomella craticulata taken in the same direction as 

 that represented in fig. 2, and showing the origin of the canals which pass 

 vertically through the solid umbilical nucleus, and whose external orifices are 

 seen at c, from the successive turns b, b, b of the spiral canal, which are seen 

 transversely divided at a. Magnified 80 diameters. 



Fig. 12. Portion of a section which has passed close to the lateral surface of one of 

 the outer whorls, in such a manner as to show a portion of its spiral canal, 

 with four of the meridional canals passing down the intraseptal spaces, and 

 giving oif successive pairs of diverging branches; between the septa from, 

 which they proceed is seen the finely-tubular substance forming the proper 

 wall of the chambers. Magnified 80 diameters. 



Fig. 13. Portion of a section passing through the median plane of the outer whorl, 

 showing some minute shells of the foraminiferous type in the cavity of three 

 of the chambers. Magnified 100 diameters. 



PLATE XVIII. 



The figures in this Plate refer to Polystomella craticulata, and to Tinoporus bacitlatus. 

 Fig. 1. Ideal representation of a specimen of Polystomella, craticulata, laid open to show 

 its internal structure : a, a 1 , a 2 , chambers of three whorls which are laid open 

 by the plane of section ; b, b\ b 2 , b 3 , septa of four whorls alternating with the 

 preceding, which are traversed by the plane of section ; c, c\ c 2 , septal aper- 

 tures ; dd\ dd', dd', meridional canals ; e, e, e, and e 1 , e 1 , e', orifices of the suc- 

 cessive turns of the two spiral canals (of which the upper one is displayed by 

 the supposed removal of the umbilical nucleus) transversely divided ; f,f, con- 

 verging canals, passing inwards from the meridional canals ; gg 1 , gg 1 , gg 1 , surface 

 of the last-formed portions of the spiral lamina, showing a row of furrows 

 passing across between the septal bands, into which the diverging canals open 

 in immediate contiguity to the septal bands ; hh', hh', older portion of the 

 spiral lamina, showing the replacement of each series of furrows by two rows 

 of punctations ; ii', ii', surface of the interior whorl, showing the obliteration 

 of the septal bands and the rows of dimpled depressions into which the 

 diverging canals open. 



Figs. 2, 3, 4, 5. External aspect of specimens of Tinoporus baculatus from Borneo and 

 Australia, showing the irregularity of their radiating prolongations. Mag- 

 nified 20 diameters. 



Fig. 6. A specimen of the same more enlarged, showing the areolated character of the 

 surface of the disk, with elevated tubercles disposed between the areolae, and 



