J. 8. GARDNER ON BRITISH CRETACEOUS NUCULIDA, Pail: 
Inst uf Specvres. 
OVATE LEVIGATZA. 
Position 
Length. Height. Depth. Pree oie er 
De planaia .....:.. ‘18 12 8 mae } 115° 
PRPROUOEG 2s ous ewe 19 13 10 ms } 128° 
NV. capseformis .... 33 21 13 ns | 128° 
N. obtusa 0.00... 1 Girhriss fa MRL Het 115° 
N. Cornueliana .... 17 12 74-10 Bran } LOM? 
N. simpler ........ 13 Ge Hee } 95° 
N. albensis ........ 16 eee ae ; 105° 
INERORIDRESSH sk oo. 5 12 9 6 aa i 85° 
Merit... g1 ae noe ie } 70° 
OVATH RETICULATA. 
N. arduennensis .... 16 12 9 i 7° 
Nadgracn aby gg a 
These dimensions are the average and not the extreme sizes in 
millimetres. The position of the umbo is stated by the percentage 
of the distance from the posterior extremity, relative to the entire 
length of the shell, at which the beak is situate. The angles are those 
formed by the hinges or superior margins, and are chiefly after 
D’Orbigny. All the species being liable to considerable variation, 
the above dimensions and figures should be regarded only as approxi- 
mate, particularly those referring to the imperfectly known Neoco- 
mian forms. 
ANGULATA. 
The Angulate are less numerous than the Ovate, and the species 
are far more isolated or distinct from each other. They appear to 
differ structurally from the Ovate ; for though the radiating structure 
so apparent in the rib-like sculpturing of certain species is invisible, 
at least externally, in others, where the shell has been abraded, it 
is very distinct internally, and is also betrayed in the crenulated 
lips. ‘The shells are angular, the umbones very prominent and far 
forward, and the lunule distinctly defined and large. 
K 2 
