236 DESCRIPTION OF THE FOSSILS. 
(Traces of spiral lines.) Septa peculiar in form ; dorsal lobe simple, and short, second 
lateral lobe acute. 
G. Gibsoni. Ph. PI. XX. fig. 13 — 18. High-Green-wood. 
Discoid, with bent acute radii prominent on the marginal and forked on the dorsal 
region. In older shells the whorls become continually more involute and gibbous, the 
young are flatter with apparent whorls. No spiral striae, a few curved constrictions. 
This remarkable fossil resembles ammonites of the oolitic formation. N. natural size, 
the others magnified three times. 
G. vesica. Ph. PI. XX. fig. 19, 20, 21. Black Hall in Bolland ; Kul- 
keagh shale. 
Subglobose, with very rounded umbilicus ; delicate transverse striae ; septa, with 
rounded and low undulations. The young differ but little. Dorsal sinuses very shallow. 
G. calyx. Ph. PI. XX. fig. 22, 23. High-Green-wood ; Black Hall ; 
Kulkeagh. 
Young, discoideo-cylindrical, glabrous, with delicate transverse strife, umbilicus 
wide, acute, (often crenate at the edges) ; volutions many ; aperture flat-lunulate, con- 
strictions direct. Septal undulations round, dorsal lobe and sinuses forming a waved 
transverse line. (The adult form is unknown to me.) 
G. mutabilis. Ph. PI. XX. fig. 24, 25, 26. 
Young, discoideo-cylindrical, glabrous, umbilicus wide acute, not crenate; constric- 
tions direct. Adult, subglobose, umbilicus rounder, narrower, constrictions direct. 
(First lateral lobe very narrow ?) 
G. Gilbertsoni. Ph. PI. XX. fig. 27 — 31. 
Depressed, outline elliptical, umbilicus small, glabrous with much bent striae. 
Septa numerous ; their lobes and sinuses round ; dorsal sinus wide and double, lateral 
sinus simple. 
G. Looneyi. Ph. PI. XX. fig. 32, 33, 34, 35. High-Green-wood. 
Depressed, glabrous, umbilicus minute, strife sigmoidal, aperture elliptical. Septa 
numerous ; the dorsal and lateral sinuses wide and double, (in young shells merely 
waved.) 
G. paucilobus. Ph. PI. XX. fig. 36, 37, 38. 
Depressed, aperture elliptical, umbilicus very small, septa with all the lobes and 
sinuses round ; the first lateral very large. (Differs from G. implicatus in the lateral 
sinus.) 
G. Henslowi. Sow. Min. Conch, t. 262. Isle of Man ; Ecton in Staf- 
fordshire ; PI. XX. fig. 39. 
Discoid, sides flat, back rounded, inner whorls exposed, septa with four lateral 
lobes and three sinuses, all sole-shaped ; dorsal sinus single, central, acute. 
