100 
PALEONTOLOGY OF NEW YORE. 
SPECIES OF THE HAMILTON GROUP. 
Bellerophon PATULUS. 
PLATE XXII, FIGS. 17-30; AND XXIV, FIGS. 3-6. 
Bellerophon patulus, Hai.l. Geology of N. Y. Surv. Fourth Geol. Dist., p. 196, fig. 1. 1843. 
“ “ “ Descriptions of New Species of Fossils, etc., p. 29. 1861. 
“ “ “ Fifteenth Rep. N. Y. State Cnb. Nat. Hist., p. 57. 1862. 
B. (Phragmostoma?) patulus, Hall. Illustrations of Devonian Fossils: Gasteropoda, plate 23. 1876. 
Shell subglobose, ventricose; umbilicus small, closed before reaching the 
centre. Volutions rounded, the last one abruptly and widely dilated, 
giving a broad subcircular aperture, the width greater than the dorso- 
ventral diameter. The lip is somewhat flattened and repand towards the 
exterior margin and broadly sinuate in front, contracted and more or less 
thickened at the postero-lateral margins, nearly inclosing and partially 
overlapping the volution on the posterior side, and extending more or less 
entirely over the columellar lip in a thickened callus, the exterior por¬ 
tion of which is pustulose. Inner margin of the columellar lip thickened 
and smooth, sometimes truncate, but usually projecting in a prominent 
boss in the centre. 
Surface, on the expanded part of the outer volution, marked by fine, close, 
concentric stri®, which are sometimes crowded in fascicles, giving an 
undulating surface; the posterior prominent part of the volution is 
marked on the back, and partially on the sides, by strong, even, arching 
cost®, which are more abruptly and sometimes subangularly curved on 
the dorsal line. These cost® sometimes continue for half the length of 
the volution anteriorly, gradually becoming obsolete on the middle and 
sides, and are never seen upon the broad expansion of the shell. The 
spaces between these cost® are marked by fine, close, concentric stri®, 
and, in well-preserved specimens, extremely fine revolving stri® are 
sometimes visible. The cost® become finer or obsolete as they approach 
the umbilicus, and the surface is marked only by the fine stri® of growth. 
I 
