206 Mr, H. J. Carter on a new Genus 



(iig. 24j b) the labyrinthic structure commences, by tlie narrow 

 pore in the centre of the tube becoming continuous, minus the 

 tube itself, with the wide irregular cavity of the labyrinthic 

 structure, till the latter ends in a contracted crevice on the 

 surface (fig. 25, a). It should be remembered that the columns 

 of the former structure are the tubes, while their cavity only is 

 ih.^ pore (fig. 24, d). 



Why, if the tubulation in Valvulina is followed by the 

 labyrinthic canals which open on the surface, should it not 

 be so with Lituola, where the labyrinthic structure exists 

 throughout ? 



Is it not, then, more consistent with nature to assume that 

 the animal parts retain their functional arrangement and con- 

 stitution although the material of the structure may be different? 

 viz. that the septal holes remain for intercameral communica- 

 tion and the tubulation of the surface for the building-up of 

 the test, whether the latter be vitreous or arenaceous, just as 

 the chambers, doors, and fenestral openings of a house would 

 differ if constructed of translucent homogeneous j)laster, instead 

 of enormous unhewn rocks of more or less opaque quartz. At 

 least such is the contrast of the two under the microscope. 



Still, it may be stated, " no openings on the surface can 

 be seen in Lituola]^^ and this has already been granted. But 

 are we to deny their existence simply because we cannot see 

 them, when, as before stated, we cannot see the sarcode and 

 the pores through which it is projected in the restless frustules 

 of Diatomaceffi during active life ? This in all probability is 

 owing to the extreme tenuity of the one and the extreme minute- 

 ness of the other. And so it may be with the Lituolida. 



In the family Nummulitida, among which, as before stated, 

 Nonionina and Operculina are included, the pores are for the 

 most part very minute — to wit, in the latter about 1 -20,000th 

 inch in diameter ; while in Textularia they are comparatively 

 large, being about l-5400tli inch in diameter, and in the 

 porcellaneous tests not discernible at all. 



But while they are large in Textularia, and equally so on the 

 surface of Valvulina, where they appear in the shape of 

 crevices between the calcareous grains of sand apparently at 

 the expense of the minute particles of cement which bind 

 together the large siliceous grains of the Lituolida, they may, 

 from their smallness, easily escape notice in the latter, al- 

 though they are perfectly evident in Valvulina. In short 

 they appear to be absent even in some species of Valvulina ; 

 but it is difficult to reconcile this as fact, although they may 

 not be visible here, when they are present in the other 

 species. 



