208 Mr. H. J. Carter on the Polytremata. 



inlet, however much (where empty, as in Dr. Carpenter's spe- 

 cimens) it may be divided into chambers by septal partitions. 

 In short, the space was conical with the base open, and so far 

 like the conical axial cavity oi Polytrema balaniforme^ if not 

 also sometimes " spiral" {torn. cit. p. 728, footnote). 



When we come to the cavities of the test outside the cone, 

 we find that those of the chambers (" chamberlets ") and those 

 of the interstices of the reticulated structure (" labyrinthic 

 system "), including the "radiating tubes," are empty in some 

 and filled up by colourless transparent calcspar in other parts. 

 Of what, then, was the fibre of the reticulated structure 

 composed ? for the whole test was formed of it. 



That Parkeria was a species of Foraminifera can hardly be 

 doubted ; but one of the chief characters of the Foraminifera 

 is their foraminated arese, of which the so-called " nummuline 

 tubulation" is an example 5 and the existence of this in Parkeria 

 has hitherto not been demonstrated. 



Now this structure, which fills the interstices of the reticu- 

 lation in Polytrema miniaceum as well as in P. halcmiforme^ is 

 so thin that it is often broken away, and moreover, with the 

 exception of the surface, often disappears altogether in P. mini- 

 aceum, as I have above stated, leaving a simple mass of reti- 

 culated fibre in the interior, which, under these circumstances, 

 becomes analogous to that of Parkeria. 



Thus, if we suppose the reticulated fibre of Polytrema 

 ininiaceum to have been converted by fossilization into calc- 

 spar, and coated with a granular crystallization of a yellowish 

 calcareous material, we should have the same composition as 

 that which appears to me to exist in the fibre of Parkeria. 

 Or the reticulated fibre of Parkeria might have been always 

 hollow, as the radiating pillars in the young test of Polytrema 

 miniaceum^ which here, however, afterwards become solidified, 

 also as above stated, in which case the coating might origi- 

 nally have been organic. 



Be this as it may, one object in introducing Parkeria here 

 (which otherwise appears to have been so well described 

 and illustrated by Dr. Carpenter, lac. cit.) is to state that 

 the coating on the surface of the reticulated fibre of this 

 fossil appears to me not to be composed of " sand," but of 

 a granular crystallization of calcareous material. 



My attention was first called to this by observing that in 

 the composition of the fossilized test of Parkeria there were 

 only nine parts of silex in a hundred, the rest being chiefly 

 calcareous material, also that in some parts, according to 

 Dr. Carpenter [torn. cit. p. 732), the angular sand-grains were 

 fitted together with " marvellous exactness," and that in my 



