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



rescent test combined with a pink or crimson colour and 

 superior apertures ; while internally it differs from most Fora- 

 minifera in possessing a cancellous structure void of the canal- 

 system, but permeated with cavernous excavations communi- 

 cating with the apertures, and more or less filled with sponge- 

 spicules and other foreign objects. The ovular and earliest 

 stages of embryonic development I have not seen. 



Having ground down a horizontal section of Polytrema 

 miniaceum to extreme thinness and mounted it in balsam, I 

 observe that the reticulated structure, together with the forami- 

 nated laminaj, which have become consolidated as already 

 mentioned, is all pervaded by crooked, branched, anastomosing 

 tubes, which appear to have been produced by the mycelium 

 of a fungus or saprolegneous organism that pervades in like 

 manner the old horny fibre of sponges and tlie reticulated 

 calcareous structure of old coral, &g. 



Poly tremabalam forme, Carter, 1876, = Cmyentert'ajGv&y, 1858. 

 PL XIII. figs. 7-10. 



Test fixed, solitary or grouped (fig. 7). Composition calca- 

 reous. General form obtusely conical, open at tlie summit 

 (fig. 7, a a), from which grooves descend in a somewhat gyrate 

 direction to the circumference, so as to leave triangular inter- 

 spaces which are slightly convex and, extending a little beyond 

 the ends of the grooves, impart a lobed form to the circular 

 base. Aperture single, at the summit (fig. 7, a a), spiral in 

 form and smoothly marginate. Colour light grey. Surface 

 uniformly even except where grooved, presenting a subhexa- 

 gonal network of smooth depressed lines more or less covered 

 by slightly convex foraminated interstices. Internal structure 

 cancellous, like that of Polytrema miniaceum, laminate, exca- 

 vated throughout by compressed triangular cavities sloping 

 from the vertical axis of the cone to the circumference, defined 

 by distinct septa or ridges laterally, supporting the foraminated 

 lamina externally, while they rest on the preceding one inter- 

 nally, commencing in the cancellated structure of the circum- 

 ference by gutter-like spaces separated by distinct septa like 

 the foregoing, which diminish in number as the triangular 

 cavity becomes narrowed upwards, until ceasing altogether it 

 opens into the hollow central axis. Hollow axis commencing 

 in a point at the centre of the base, and gradually increasing 

 in size upwards till it reaches the aperture at the summit, 

 spiral in form, and receiving the openings of the triangular 

 cavities successively as it progresses upwards. Triangular 

 cavities also commencing at the same point, increasing in size 



