400 
ME. W. K. PAEKEE AND PEOFESSOE T. E. JONES ON SOME 
slight attempt to modify it by subsidiary pores in Nummulina is sufficient to indicate an 
inability to depart from a special plan. The feebler Polystomellce ( Nonionince ) are, with 
their neat shell and simple aperture, isomorphic with some Nummulince, especially if we 
compare some of the more strongly limbate of the former with the small “ Opercu- 
line ” or “Assiline” varieties of the latter ( Nonionina limba compared with Operculina 
ammonoides) ; but the shell-tissue is more dense and tubuliferous in the latter (as in 
Nummulina proper), and the perfect marginal rim and the canal-system are wanting in 
the former. 
Again, both in some of its higher [Polystomella macella ) and lower forms ( Nonionina 
turgida) Polystomella loses its horizontal symmetry, which Nummulina (except in some 
Operculine individuals) never does ; the asymmetrical ally of Nummulina ( Amphiste - 
gina) being sufficiently differentiated as to canal-system and other points to be regarded 
as specifically distinct. 
The close linking of Nonionince with Polystomella , especially by means of the gra- 
duated subdivision of aperture, and modification of lateral fossettes, retral processes, 
and septal bridges, is too strong to be in any way antagonized by the merely isomor- 
phic resemblances of the former with Nummulina ; and “Nonionina” is rightly sup- 
pressed as a generic term, being merged in “ Polystomella,” which well represents the 
peculiar features of the fairly developed, but not exaggerated, natural type. See Ann. 
Nat. Hist. 3rd ser. vol. v. p. 103, &c. ; Carpenter’s 4 Introduct.’ p. 286, &c. 
Scheme of the Polystomella. 
A. Canal-system, retral processes of the chambers, and the septal bridges and apertural bars, all highly developed. 
Polystomella eraticulata, Fichtel and Moll, sp. 
B. Canal- system feebly developed ; hut the retral processes, septal bridges, and apertural bars perfect. 
P. ceispa, Linn., sp. P. strigillata, Fichtel and Moll, sp. 
P. unguiculata, Gmel., sp. P. macella, Fichtel and Moll, sp., &c. 
C. Canal-system, the septal bridges, and apertural bars -well-developed, but the retral processes abortive. 
P. Arctica, Parker and Jones. 
D. Canal-system and retral processes feebly developed, but the bridges over the septal lines and the bars across 
the aperture perfect. 
P. striatopunctata, Fichtel and Moll, sp., and P. Faba, Fichtel and Moll, sp. 
E. Canal-system, retral processes, septal bridges, and apertural bars all abortive more or less. 
Nonionina limba, D’Orb. N. stelligera, D’Orb. 
N. asterizans, Fichtel and Moll, sp. N. Scapha, Fichtel and Moll, sp. 
N. depressula, Walker and Jacob, sp. 
F. Canal-system, retral processes, septal bridges, and apertural bars all obsolete: there may, however, be gra- 
nular shell-growth on the umbilici. 
N. granosa, D’Orb. N. umbilicatula, Montagu, sp. N. turgida, Williamson, sp. 
