FUSIDA. 131 
MESORHYTIS, Meek. Shell agreeing nearly with Peistocheilus 
in form, but with plaits of columella stronger, comparatively 
little oblique, and exposed directly opposite the middle of the 
aperture ; surface with fine spiral striew, and vertical costae. F. 
gracilenta, Meek (xlviii, 88). Cretaceous; Yellowstone River, 
150 miles from its mouth. Has the folds of a Mitra, rather than 
a Fasciolaria, and Meek refers it with considerable doubt to its 
present position. 
CRYPTORHYTIS, Meek. Shell generally under medium size, with 
volutions convex, but constricted above, and provided with 
regular vertical costz or small folds; plaits of the columella 
very oblique, not exposed in a direct view into the aperture, and 
occupying a higher position than in the typical group; outer lip 
smooth within. #. Cheyennensis, Meek and Hayden (xlviii, 89 
from a cast). Cretaceous ; Dakotah. 
LIROSOMA, Conrad. Subpyriform; ribbed, beak narrow and 
produced, slightly recurved; one long, very oblique plait at the 
angle of the columella. /. sulcosa, Conrad (xlviii, 90). Miocene; 
Maryland. 
FASCIOLINA, Conrad. Fusiform; columella nearly straight to 
the extremity of the beak; one prominent oblique fold on the 
columella, situated above the middle of the aperture. F’. Woodii, 
Gabb. Miocene; New Jersey. The only figure does not exhibit 
the aperture, but Conrad states that the fold is situated more 
remote from the beak than in any other genus except Cuma. 
7) 
SupramMity PTYCHATRACTINZ. 
This group was distinguished as a family by Stimpson. The 
shell of Ptychatractus unites the form of a Sipho with the folds 
of a Fasciolaria; its small size, color, and northern habitat 
will distinguish it from the latter, even without taking into 
account the very diverse dentition ; yet without the latter differ- 
ence it would scarcely have been advisable to have separated 
the single species upon which the genus was founded from 
Fasciolaria. 
PTYCHATRACTUS, Stimpson, 1865. 
Distr.—3 sp. Boreal Atlantic and Pacific. P. ligatus, 
Mighels and Ads. (xlviii, 91). 
Shell fusiform, spirally striated; aperture with a moderate 
canal; columella plicated as in Fasciolaria. 
MeyertiA, Dunker and Metzger. 
Syn.—Metzgeria, Norman. 
Distr.—M. alba, Jettreys (xlviii, 92). Faroé Is., North Sea, 
Norway. 
Shell elongate-fusiform, longitudinally obtusely plicate ; spire 
