24 MALACOZOA. CEPHALOPODA. 



Genus 2. Nummulina. — Shell discoid, with a pluri- 

 locular spire in the same plane ; the two surfaces convex, 

 the margin thin. Nummus, money ; like a coin. Lamarck. 



1. Nummulina marginata. — Shell discoid, convex on 

 one side, conico-convex on the other, with a very thin 

 broad margin. Marginatus, edged. 



Genus 3. Discorbis. — Shell discoid, spiral, many- 

 celled ; the upper surface occupied by the last-formed 

 whorl. Discus, a disk ; drbis, a ball. Lamarck. 



1 . Discdrbis lobdtulus. — Shell generally roundish, 

 convex above, with the centre depressed ; the last or 

 upper turn of several convex frosted lobes. Name from 

 Idbus, a lobe. 



Var. The shell reversed. 



Genus 4. Rotalia. — Shell discoid, spiral, many-celled ; 

 the lower surface occupied by the last-formed whorl. 

 R6ta, a wheel. Lamarck. 



1 . Rotalia JBeccdrii. — Shell orbicular, depressed, con- 

 vex above ; of four or five obliquely lobate turns, the 

 last with about twelve lobes. Named after Beccaria, an 

 Italian philosopher. 



Var. The shell reversed. 



Genus 5. Spiroloculina. — Shell suborbicular, de- 

 pressed, with the cells curved, and opposed to each other 

 in a single plane, and completely exposed, or not em- 

 bracing each other. Spira, a whorl; loculus, a cell. 

 D'Orbigny. 



1. Spiroloculina concentrica. — Shell suborbicular, de- 

 pressed, concave on both sides. Concentricus, disposed 

 round a centre. 



Genus 6. Vermiculum. — Shell roundish, depressed, 

 of few cells, alternately folded upon each other. Ver- 

 micula, a little worm. Montagu. Miliola of Lamarck. 



1. Vermiculum subrotundum. — Shell orbicular, de- 

 pressed, of three glossy white turns ; the mouth tooth- 

 less. Subrotundus, roundish. 



