MOLLUSCA. 
.383 
Lenticulites rotulata. —The Rolled Lenticulites. 
Plate LXXXIII. fig. 15. 
Orbicular; margin acute; disc globular. Fossil at Mendon. 
Genus 19.—R O T ULITE S. — Lamarck. 
Generic Character. —Shell orbicular, multilocular, spiral, con¬ 
vex, or conical, above ; flat, radiated, and tubercular beneath ; 
aperture marginal and trigonal. 
Rotulites trochidiformis. —The Trochus-Shaped Rotulites. 
Plate LXXXIII. fig. 16. 
Shell conoid; volutions carinated; lower one granulated. 
Fossil at Grignon. 
TRIBE IV.-SPHERULACEA. 
Shell globular, spheroidal, or oval; with the volutions mutu¬ 
ally enveloping, or the cells contiguous, and forming a tunic. 
Genus 20.—MELONIA.— Lamarck. 
Generic Character. —Shell subspherical, multilocular; spire 
central; volutions contiguous, convolute, tuniciform ; cells nu¬ 
merous, narrow; septa imperforate. 
Melonites sphceroidea. — The Round Melonia. 
Plate LXXXIII. fig. 17. 
Entirely globular, and divided by compressed ribs. Fossil. 
Genus 21. — GTROGONA.— Lamarck. 
Generic 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 medicaginula. 
Somewhat spherical, with transverse keels, and a spiral extre¬ 
mity. Fossil at Montmorency. 
Genus 22.—MILIO L A. — Lamarck. 
Generic Character. —Shell transverse, ovate-globular, or elon¬ 
gated, multilocular ; having transverse cells surrounding the axis. 
