86 WINCHELL AND MARCY ON FOSSILS FROM THE 



the base, while the upper end is convex. The whole exterior is divided into small rhomboidal 

 or nearly square areas by ridges which originate at the apex and describe curves obliquely 

 approaching the base, and crossing each other like the curves of the " engine-turned 

 ornament of a watch." In the best preserved specimens, these ridges are surmounted by 

 little crests deepening the pits or cells which they mark out. In other specimens these 

 cells are simply hopper-shaped cavities. The cells of course increase in size from the ori- 

 gin of the ridges to that part of the surface where the diameter of the body is great- 

 est. In the bottom of each cell is a small pore penetrating the internal cavity. Besides 

 this, each cell communicates by pores with the four neighboring cells touching it at the 

 angles. These connecting pores are parallel with the general surface, and pass under the 

 intersection of the two crests or ridges. Each rectangular intersection, therefore, rests over 

 the crossing of a couple of right-angled passage-ways. In some specimens, in which the 

 hopper-shaped cells are shallow, these pores, extending across the cell from corner to corner, 

 present the appearance of open passage-ways excavated through the substance of the test ; 

 on the side toward the larger end of the body, however, the passage-way remains covered. 

 In such cases, the feature which first strikes the eye is a pair of furrows intersecting each 

 other at right angles in the middle of each cell, forming three sides of a cross. 



Our specimens are all casts, and exhibit no further internal structure, except that the 

 central pores can be seen penetrating the internal cavity, and losing themselves at the 

 depth of a quarter of an inch. Polished sections at right angles with the surface present 

 obscure indications of sac-like cells extending inward from the surface about one fourth 

 of an inch. There is one of these on each side of the central pore, and the inner end 

 of the cell is regularly rounded. The pore seems to have been the means of communi- 

 cation between the inner common cavity of the body and the external element. It was 

 perhaps respiratory in its function. The cells present the appearance of individualization, 

 while the entire body was undoubtedly a compound organism. Polished surfaces at right 

 angles with the larger axes of these cells do not succeed in bringing their walls into view. 



No peduncle of attachment appears to have been in connection with the smaller end ; but 

 the larger ends are all imperfect, and it seems not unlikely that this end was adherent, or 

 possibly pedicled. 



The largest and most perfect specimen is 2.5 inches in length, with a maximum diameter 

 of 1.75 inches. The diameter of the cells over the most swollen portion of the body is .09 

 inch. 



These very interesting and beautiful specimens are evidently congeneric, if not conspecific 

 with I. K&nigi Murchison, 1 and I. canadensis Billings, (Geol. of Canada, pp. 309, 327,) though 

 the entire form of I. canadensis has not been figured, and I. Komigi is less attenuate at the 

 smaller end. We are of the opinion, also, that they possess close relations with Dictyocrinus 

 Conrad, and Tetragonys Eichwald; and that all these genera belong to the same zoological 

 type as Reccptaculites, which has been shown by Salter to be one of the Foraminifera, as D. D. 

 Owen conjectured in 1844. At least, the affinities of Ischadites with Receptaculites seem to 

 be pretty clearly shown by our specimens ; and it is worthy of remark that Morris, in his 

 Catalogue, has united I. Kwnigi and Receptaculites Neptuni, while Professor Hall says, (Pal. 

 N. Y., HI. p. 148) : " The figures [of I. Kceniyi] in the Silurian System bear so close a resem- 

 blance to Receptaculites that I could scarcely regard them as distinct from that genus." 



1 Silurian System, 697, pi. xxvi. fig. 11 ; Siluria, pi. xii. fig. 6. 



