﻿118 CARBONIFEROUS AND PERMIAN FORAMINIEERA. 



Stacheia polytrematoides, nov. PI. IX, figs. 10 — 13. 



Characters. — Test adherent, irregular in growth and outline; composed of a 

 multitude of minute chambers, either confused or arranged in more or less regular 

 layers ; forming encrusting masses of uneven thickness, spreading over the surface of 

 foreign bodies, sometimes swelling into mammillate or arborescent protuberances which are 

 pierced at the top with large orifices. Surface areolated, blistered or granular. 

 Dimensions indefinite; in patches usually less than \ inch (6 mm.) in diameter. 



The relation of Stacheia polyirematoides to the other members of the genus may be 

 seen by a comparison of two specimens such as those represented by figs. 8 and 9, PI. IX, 

 the former being taken from a good example of S. acervalis, the latter from a specimen, 

 somewhat similarly circumstanced, of S. polyirematoides. Notwithstanding a certain 

 resemblance in external contour, considerable difference exists between the two ; for, whilst 

 S. acervalis has a few, large, distinct chambers, which are subdivided into chamberlets, 

 S. polytrematoides consists of a wild-growing mass of small chambers sometimes disposed in 

 layers, but more frequently arranged in no particular order, spreading indefinitely over 

 the surface of any object to which it has attached itself. In other words the distinction 

 rests between the large-chambered, Plaworbulina-\ike habit of the one form, and the 

 small-chambered, confused, Polytrema-Xike growth of the other. Morphologically speaking 

 the analogy that exists between Stacheia polyirematoides and corresponding organisms in 

 the porcellanous and perforate series, namely, Nubecularia and Polytrema, is very striking ; 

 but, rather than occupy space with the repetition of details, I would refer the student, as 

 I have already done on a former page, to Dr. Carpenter's excellent account of these 

 types, 1 for the explanation of many of the singular and apparently anomalous features of 

 the present species. It has been found very difficult to obtain transparent sections of the 

 Carboniferous organism, showing its internal structure with any degree of distinctness, 

 but Mr. Hollick's drawing, from a fairly good preparation, PI. IX, fig. 13, is sufficient 

 to demonstrate that the analogy to Polytrema is borne out in interior arrangement as well 

 as in external configuration. I have not been able in any case to detect true shell-perfora- 

 tion, that is to say, such tubulation of the shell-wall as is characteristic of the hyaline 

 Foramiuifera. Some specimens at least show a more or less composite structure of the 

 test, with embedded sand-grains of appreciable size, but in the majority of cases the 

 investment is nearly smooth, and its minute structure is partly assumed from analogy 

 to closely allied forms in which the arenaceous character is more distinctly traceable. 

 Distribution. — In England and Scotlanda like, Stacheia polyirematoides has been 



1 ' Introd. Foram.,' pp. 71 and 235, et seq. 



