470 ORIGINAL ARTICLES. 



group together the whole aggregate of " imperforate" genera under 

 the three families Gromida, Miliolida, and Lituolida. The family 

 Gromida presents in Lieberhiihnia the nearest approach to a naked 

 representative of this Order ; the membranous envelope of its sarcode- 

 body being reduced to such extreme tenuity, as only to be distinctly 

 visible where it surrounds the pedicle, from which the pseudopodia 

 are given off; but it is not a little remarkable, and is very significant 

 of the physiological value of the character, that notwithstanding the 

 absence of any shelly wall to limit the extension of the sarcode-body 

 into pseudopodia, these are just as much restricted to one region as if 

 the body had been entirely shut up within an envelope pervious only 

 at one spot. In Gromia, the membranous envelope is of greater firm- 

 ness, and presents a wide aperture ; and the physiological condition of 

 its animal so closely corresponds, except as regards the segmentation 

 of the body, with that of the animal of Miliola, that I cannot see any 

 ground for separating (as M.M. Claparede and Lachmann have done) 

 the Gromida from the Poraminifera proper. Thus I am led to regard 

 Gromia as the unilocular type of the imperforate series ; holding the 

 same place in it that Lagena and Orbulina do in the perforated. 



The family Miliolida includes an extensive range of generic forms, 

 from the simple undivided Comuspira (the Spirillina foliacea of Prof. 

 "Williamson) to the highly complex and minutely-subdivided Orbito- 

 lites. But all these forms are so intimately united with each other, 

 as to constitute an extremely natural assemblage. They all agree in 

 the possession of an imperforate calcareous shell, the substance of 

 which is " porcellanous," being opaque-white by reflected light, and 

 brownish-yellow when sufficiently thin for light to be transmitted 

 through it. The wall of this chamber is simply joined on to that 

 which preceded it, so that the septa between the cavities of adjacent 

 chambers are single, being composed merely of the portions of the 

 walls of the older chambers, which are embraced by the newer. The 

 communications between the successive chambers, and between the 

 last chambers and the exterior (whether formed by a single large 

 aperture as in Miliola, or by the multiplication of smaller pores as in 

 Peneroplis,) are very free ; having to give passage not merely to 

 stolons which are subservient to the multiplication of segments, but 

 to bands of sar code-sub stance large enough to transmit with facility, 

 to the segments that are furthest removed from the exterior, the nutri- 

 ent materials obtained by the pseudopodia which issue from the last 

 alone. Neither " intermediate skeleton," nor " canal-system" for its 

 nutrition, presents itself in the Poraminifera of this family ; although 

 a sort of representation of it exists in the most complex form of that 

 very aberrant type Dactylopora, which, in addition to the aggregate 

 of separate chambers, has a deposit of solid shell-substance, traversed 

 by a regular system of passages that has no communication with the 

 chambers, but seems to have been in connection with a sarcode-body 

 outside of them. 



We occasionally find among the Miliolida that the surface of the 

 shell is formed of arenaceous particles ; but these are embedded in a 



