EXPLANATION OF THE PLATES. 589 



the furrowed surface of the terminal portion of the radiating prolongations. 

 Magnified 40 diameters. 



Figs. 7, 8, 9, 10. Specimens of the Philippine variety of Tinopoms baculatus, showing 

 the variability of their form. Magnified 12 diameters. 



Fig. 11. Fragment of Polystomella craticulata, showing the furrowed internal surface of 

 three of the chambers, a, a 1 , a 2 , the furrows being deepest at the posterior 

 margin for the reception of the retral processes ; whilst at bb l , bb*, are shown 

 two of the meridional canals laid open by the fracture of the septa which 

 contained them, with the series of orifices of the diverging canals which pass 

 oif beneath the ridges that intervene between those furrows. Magnified 40 

 diameters. 



Fig. 12. Internal cast of the chambers and canals of Polystomella craticulata, repre- 

 senting the form of the body and the distribution of the canal-system: 

 , retral processes, proceeding from the posterior margin of one of the 

 segments ; b b', smooth anterior margin of the same segment ; c, cf, stolons 

 connecting successive segments, and uniting themselves with the diverging 

 canals*; d, d l , d 3 , three turns of one of the spiral canals; e, e\ e*, three 

 of the meridional canals ; /, f 1 , f, their diverging branches. Magnified 40 

 diameters. 



Fig. 13. Fragment of a similar cast, showing a portion of three segments on their 

 internal aspect, with their connecting stolons, c, two of the meridional canals, 

 ed, and their diverging branches f,f. Magnified 40 diameters. 



PLATE XIX. 



All the figures in this Plate refer to Calcarina SpenglerL 



Fig. 1. Disk of Philippine variety, as seen on the side nearest the apex of the spire, with 

 the origins of the spines; showing the minute punctations and scattered 

 tubercles of the surface of the disk, and the furrowed surface of the spines; 

 the spire not anywhere apparent. Magnified 20 diameters. 



Fig. 2. Disk of Maltese variety, as seen on the same side, showing the entire length 

 of the spines, which in this specimen are unusually numerous and tend to 

 subdivide at their extremities; no markings of any kind are seen on its 

 surface, nor is the spire in the least apparent. Magnified 20 diameters. 



Fig. 3. Disk of Philippine variety, as seen on the same side, with the origins of the 

 spines, showing the punctations of the disk and the furrowing of the spines, 

 with an unusual abundance of semitransparent tubercles ; the spire not any- 

 where apparent. Magnified 20 diameters. 



* This portion of the figure is ideal ; and by a misapprehension on the part of the artist, the segments 

 of the inner whorl have been made to range with those of the outer whorl, instead of alternating with them 

 which seems to be the typical arrangement, though often departed from. 



