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GENUS FABULAEIA. 83 



chamber, instead of being an empty space, is partly occupied with soUd shell-substance, 

 which is so disposed as to divide it into a great number of capillary tubes, whilst its aperture, 

 instead of being single, is made up of numerous minute pores. 



117. External Characters. — The general aspect of Fabularia (Plate VI, fig- 37, a, b) 

 so remarkably resembles that of a gigantic BUumlina, as to occasion some surprise that the 

 true relationship of this type was not earlier recognised. In fact, it externally differs only in 

 size, — often attaining a length of 0'24 inch, and a breadth of 0-18 inch, thus far exceeding 

 the largest Mlliu/ce in dimensions, and in the cribriform character of its aperture, in which 

 it agrees with //««mH« (f 112). Very commonly, however, the peculiar structure of its 

 interior is partly disclosed by the abrasion of the surface, which lays open the superficial 

 series of the longitudinal canals into which it is divided. 



118. Infernal Structure. — The internal structure of Fabularia may be made out very 

 tolerably by the examination of specimens fractured in different directions ; but the most 

 satisfactory elucidation of it is obtained from thin sections, especially from such as are 

 carried in a direction transverse to the longitudinal axis (fig. 38). It is there seen that its 

 general plan of growth is distinctly " biloculine;" the walls of the principal chambers on the 

 two sides of tlie longitudinal axis meeting each other along the line a b, just as they do in 

 Fig. XVI, B (p. 78). But the cavities of these chambers, instead of being hollow, are filled up 

 with sohd shell-substance, which is perforated by channels whose general direction is 

 longitudinal, though these are often connected, like the Haversian canals of bone, by channels 

 passing in a transverse or oblique direction. The longitudinal channels are arranged with, 

 some approach to regularity ; a row of small orifices being observed to lie just within the 

 external boundary of each chamber, and thus corresponding with the layer of closely 

 approximated canals which is brought into view when the surface of the shell is removed by 

 abrasion (fig. 37, a), whilst a much larger set of orifices, less regularly arranged, nearer to the 

 internal portion of the chamber, shows that the channels are there much wider, but neither so 

 numerous nor so closely approximated. The whole system of channels, whose mutual 

 inosculations bring every part of it into the freest communication with the rest, terminates at 

 the septal plane in a cribriform aperture (fig. 37, b), resembling that which is normal in 

 Ilaurrina {^^ l\2), and occasional in yI/27zo/« mxoriim (^110). Another curious feature of 

 relationship to this last variety of the Milioline type is presented in the very deep pitting by 

 which the external surface of each chamber is not unfrequently marked (fig. 38, b). This 

 pitting is afterwards filled up by the calcareous deposit which occupies the cavity of the 

 chamber formed around it ; so that the innermost layer of this deposit comes to be furnished 

 with a corresponding set of minute tubercles (fig. 38, a), which may be brought into distinct 

 view by so fracturing a specimen as to separate this layer from the wall of the penultimate 

 chamber on which it was moulded, and from which it may be commonly detached without 

 difficulty. The manner in which these pits and tubercles are mutually appUed to one another 

 (like the pits on the under side of the epidermis to the papillae of the cutis vera), is seen in 

 section in fig. 38, a', along the line a b. 



1 1 9. Affiniticis. — The genus Fabularia may be considered as presenting the culmination 



