60 CEPHALOPODA. 



gins ; spire internal, discoid, multilocular, covered over by seve- 

 ral tables ; the outer partitions complicated, produced, extending 

 and uniting on each side of the centre ; cells very numerous, 

 small, alternate, and formed by transverse imperforate septa. 



Nnmmulites complanatus. — The Flat Nummulites. Plate 

 X. fig. 9. Orbicular, broad, depressed at the sides, and smooth ; 

 margin undulated. One and a half inches long. Fossil in 

 France. 



Ge7iusl3.—V0RTICIALIS.— Lamarck. 



Generic Character. — Shell discoid, spiral, multilocular j volu- 

 tions contiguous, but not appearing externally; septa trans- 

 verse, imperforate, but not extending from the centre to the cir- 

 cumference. 



Vorticialis strigilata. — The Creased Vorticialis- Plate 

 X. fig. 9. Somewhat depressed, transversely ribbed, and spirally 

 striated. Fossil. 



Genus M.—POLYSTOMELLA.— Lamarck. 



Generic Character. — Shell discoid, multilocular, with invisi- 

 ble volutions ; with numerous transverse ribs ; aperture formed 

 by variously disposed holes. 



Fohjstomellacrispa. — The Wrinkled Polystomella. Plate 

 X. fig. 11. Slightly wrinkled, and ribbed transversely. Found 

 fossil in the chalk formations. 



Genus 15.— SIDEROLITES.— ZawiarcA'. 



Generic Character. — Shell discoid, multilocular; volutions 

 contiguous, but not visible externally; the disc convex on both 

 sides, and studded with tubercular dots ; the circumference mar- 

 gined with unequal radiating lobes ; septa transverse, imperfo- 

 rate ; aperture distinct, somewhat lateral. 



Siderolites calcitrapoides. — The Chalk Siderolites. Plate 

 X. fig. 1. With four lobes, and punctated throughout. Fossil 

 in the mountain of St Peter, at Maestricht. 



Genus 16.— DISCORBIS.— /:amarc^. 



Generic Character. — Shell discoid, spiral, multilocular, with 

 simple partitions ; the volutions wholly visible, exposed, and 

 contiguous ; with transverse, numerous, and imperforate septa. 



