DK. SCHULTZE, ON THE RHIZOPODA. 151 



chambers very narrow, embracing or 

 not. Numerous openings, scattered over 

 the whole of the anterior wall of the 

 last chamber ; or, instead of these, a 

 large opening produced by the coales- 

 cence of numerous smaller ones. 

 Gen. Peneroplis, Dendritina, Vertebralina, Coscinospira, Spi- 

 rolina, Lituola, Orbiculina. 

 4. Subfam. PolystomelUda. — Shell tolerably thick, colourless, trans- 

 parent, finely porous ; chambers em- 

 bracing ; the anterior wall of the 

 last chamber, besides the fine pores, 

 has either no larger opening at all, or 

 a few very minute, irregular fissures, 

 on the side towards the penultimate 

 whorl. On the surface of all the 

 chambers, rows of fissure-like, often 

 perforating depressions, running at 

 right angles to the direction of the 

 dissepiment. 

 Gen. Polystomella. 



7. Fam. Alveolinida. — Globose, ovoid, or cucumber-shaped shells, com- 



posed of spiral tubes, each resembling a Cor- 

 nuspira, and furnished with a special open- 

 ing at the end of the whorl. The tubes all 

 communicate by connecting openings, and 

 besides this, are all subdivided by incomplete 

 dissepiments, in the same manner as in the 

 Nonionina. The situation of these dissepi- 

 ments, which are but few in number, and of 

 the connecting openings, is indicated by me- 

 ridional lines, which are seen on the surface 

 of the shell. 

 Gen. Alveolina. 



8. Fam. Soritida. — Discoid, multicellular shells, exhibiting only in the 



centre an indication of a helicoid spiral, otherwise 

 cycloid ; that is, growing uniformly at the whole 

 border of the disc. The brown, transparent, 

 finely porous shell, is formed of minute chambers, 

 connected together in the direction of straight or 

 cui'ved radii, and at the border of the disc, each 

 presenting a large opening. 

 Gen. Sorites, Amphisorus, Orbitulites (Orbitoides, Orbitulina, 

 Phaculina, Marginopora), Cj'clolina (chambers per- 

 fectly annular, with numerous openings on the border 

 of the disc). 



2. Group Rhabdoidea. 



The chambers arching one over the other, in a straight or slightly curved 



line, in a single series. 



9. Fam. Nodosarida. — Rod-shaped shells, whose chambers are super- 



imposed one upon another in a series, and 

 communicate with each other by a large open- 

 ing ; a similar opening in the last chamber. 

 (Except in the genus ConuUna, where there 



