Maryland Geological Suevey 287 



Subgenus PATELLOSTIUM Waagen 



Bellerophon- (Patellostium) patulus Hall (?) 

 Plate XXXV, Fig. 14 



Bellerophon patultis Hall, 1843, Geol. N. Y., pt. iv, p. 196, fig. 1. 



Bellerophon paiulus Hall, 18G2, Fifteenth Rep. N. Y. State Cab. Nat. Hist., 



p. 57. 

 Bellerophon patulus, 1879, Pal. N. Y., vol. v, pt. ii, p. 100, pi. xxii, figs. 17-30; 



pi. xxiv, flgs. 3-10; pi. xxvi, figs. 10-12. 

 Bellerophon patulus Keyes, 1891, Johns Hopkins Univ. Circ, vol. xi, p. 29. 

 Patellostium patulus Ulrich and Scofleld, 1897, Geol. Minn., vol. iii, pt. ii, 



p. 854. 

 Bellerophon patulus Clarke, 1903, N. Y. State Mus., Bull. G5, p. 526. 

 Ptoniatis patulus Grabau and Shimer, 1909, N. Am. Index Fossils, vol. i, p. 



624, fig. 841. 



Description. — " Shell subglobose, vcntricose ; umbilicus small, closed 

 before reaching the center; volutions rounded, the last one abruptly and 

 widely dilated, giving a broad subcircular aperture, the width greater 

 than the dorso-ventral diameter; the lip 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 extend- 

 ing more or less entirely over the columellar lip in a thickened callus, 

 the exterior portion of which is pustulose. Surface, on the expanded 

 part of the outer volution, marked by fine, close, concentric striae, which 

 are sometimes crowded in fascicles, giving an undulating surface; the 

 posterior prominent part of the volution is marked on the back, and par- 

 tially- on the sides, by strong, even, arching costae, which are more 

 abruptly and sometimes subangularly curved on the dorsal line. These 

 costae 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 the costae 

 marked by fine, close, concentric striae, and in well-preserved specimens, 

 extremely fine revolving striae are sometimes visible. The interior cast 

 is smooth. This shell can usually be readily distinguished by its widely 

 expanded outer volution, the broad, shallow, sinuosity in the anterior 



