Mr. H. J. Carter on the Polytremata. I'Jl 



"Ebon Islands, Oceania") was examined, it was found to 

 have torn off the Polytrema entire from tlie hard object, 

 thus protecting its branched head, while the disk of its base 

 is equally well preserved ; I have been able to view the latter 

 through a 1-inch object-glass and make the accompanying de- 

 lineation. The whole disk, Avhich is circular, measures about 

 5-48ths inch in diameter, of which the figure represents about 

 2-48ths inch of the centre (fig. 2). This portion, which only 

 in its outer part bears indication of the cyclical arrangement 

 of chambers, not an uncommon sequel (as before stated) to 

 the spiral commencement common to and most obvious in the 

 discoid Foraminifera, presents a confused centre (fig. 2, a), 

 beyond which come three circular rows of radiating lines 

 (fig. 2, Z*), which, from their quadrilateral interspaces, would, 

 in Orbitoides dispansa &c., represent as many chambers of 

 the central plane (^Annals,' 1861, vol. viii. pi. xvi. fig. 1,^), 

 but here are covered in by a basal chitinous layer of unfora- 

 minated sarcode, Avhich was the bond of union between the 

 Polytrema and the hard object on which it grew, and Avhich, 

 on having been partly removed over one row (lig. 2, c), brings 

 into view a continuous, apparently circular, ring-like cavity 

 with foraminated roof sloping in towards the centre of the 

 specimen ; so that the resemblance to the chambers of the 

 central plane in Orhitoides disjjansa does not appear to go be- 

 yond the " three circular rows of radiating lines with quadri- 

 lateral interspaces." 



Leaving this unique specimen, which only illustrates this 

 point, and going to the superstructures of Polytrema generally, 

 we observe that its resemblance to Orhitoides dispansa is no 

 longer traceable ; for when we come to the continuous conical 

 solid pillars of shell-substance, whose large ends are so con- 

 spicuous on the surface of the latter, and are the same in Tino- 

 porus hacidatus and Comdites Cooki, Garter, ^^Patellina (Car- 

 penter), it will be found that there are none. The unforami- 

 nated as well as the foraminated dimples in the foraminated 

 portion of the surface of Polytrema (fig. 6, g, i) only indicate, 

 as before mentioned, hollow structures which in the early part 

 of life support the foraminated layers (fig. 3). Hence Dr. 

 Carpenter's " aggregation of calcareous substance into solid 

 pillars [h h) exactly resembling those which have been seen in 

 T. hacidatus and mPatellina Cookt^^ (Introduction, p. 286) is 

 imaginary. The unforaminated dimples on the surface of 

 Polytrema which most resemble the ends of the " solid pillars " 

 alluded to are the ends of short, interrupted, cylindrical pillars, 

 in some parts foraminated at both ends, which, it is true, give 

 support to the spans or arches of the undulating foraminated 



