GO CEPHALOPODA. 



gins ; spire internal, discoid, nnultilocular, 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. 



Nummulites 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. 



Geims 13.~V0RTICIALIS — Lamarck. 



Generic Character. — Shell discoid, spiral, multilocular ; 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 U.— POLY STOMELL A.— ZawiarcA-. 



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

 ble volutions ; with numerous transverse ribs ; aperture formed 

 by variously disposed holes. 



Polystomella crispa. — The Wrinkled Polystomella. Plate 

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

 fossil in the chalk formations. 



Genus 15.— SIDEROLITES— XaT/iarcA. 



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.— Aan.-arcA. 



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

 simple partitions ; the volutions wholly visible, exposed, and 

 contiguous ; with transverse, numerous, and imperforate septa. 



