62 CEPHALOPODA. 



central ; volations contiguous, convolute, tuniciform ; cells nu- 

 merous, narrow ; septa imperforate. 



Melonites sphceroidea. — The Round Melonia. Plate X. 

 fig. 17. Entirely globular, and divided by depressed ribs. 



Fossil. 



Genus 21 — GYROGONA.— ZamarcA. 



Geveric Character. — Shell spherical, concave within, com- 

 posed of linear, curved, canaliculate pieces ; the external surface 

 with carinated, parallel, partly transverse ribs, and bound at the 

 last volution ; aperture round, terminated by a small round shell. 



Gyrogonites medicaginulo . Somewhat spherical, with trans- 

 verse keels, and a spiral extremity. Fossil at Montmorency. 



Genus 22.— MILIOLA.— ZawiarcA. 



Generic Character. — Shell transverse, ovate-globular, or elon- 

 gated, raultilocular ; having transverse cells surrounding the axis, 

 and alternately surmounting each other ; aperture very small, 

 orbicular or oblong, situated at the base of the last volution. 



Miliola ot-a^a.— The Oval Miliola. Plate X. fig. 18. 

 Ovate, small, with an oblong-ovate aperture. Fossil at Grig- 

 non. 



FAMILY V. — CRISTACEA. 

 Shell semidiscoid, with an eccentric spire. 



Genus 23 — ORBICULINA Lamarck. 



Generic Character. — Shell subdiscoid, multilocular ; spire 

 eccentric ; volutions contiguous and compound ; chambers short 

 and numerous ; septa imperforate. 



Orbiculina vncinata — The One Sinused Orbtculina. Plate 

 X. fig. 19. Spirally striated, and the volutions separated by a 

 deep sinus. Fossil. 



Genus2^. — CRlSTEhL ARIA.— Lamarck. 



Generic Character. — Shell semi-discoidal, multilocular ; cham- 

 bers contiguous and simple, progressively enlarging ; spire eccen- 

 tric, subulate ; septa imperforate. 



