1^89 ] Soleniscus : Its Generic Character. 423 
having the shell fusiform or subovoid ; the spire always acute; 
body whorl relatively rather large ; aperture suboval, rounded 
anteriorly, angular behind ; labrumthin; columella imperforate, 
and provided with a more or less distinct fold; surface 
smooth. 
As observed by White, the twisted ridge on the columella 
is scarcely discernible in the perfect shell until the outer lip is 
broken away, when it is seen to become more and more pro- 
nounced as it passes inward from the aperture. By the re- 
moval of the lip the anterior portion of the shell seems more 
extended than in the unbroken specimen; and this feature 
was made unduly conspicuous by Meek and Worthen when 
they established the genus under consideration. Although 
seldom noticed on account of the apertural part of the shell 
being filled with matrix, a more or less well defined columellar 
fold is observable in the most of the hitherto called Macrochei- 
li. This plication, very slightly developed in some forms, 
passes, in the various species, by imperceptible gradations into 
a conspicuous revolving ridge as exhibited in 5. typicus. The 
callus of the inner lip varies so greatly, according to the state 
of preservation and the locality, that only in a general way can 
it be relied upon as of generic importance. 
The following species, originally described as Macrocheilt 
may be considered as properly belonging to Soleniscus: 
5. typicus M. & W. S. (?) attenuatus Hall. 
. acutus Sow. 
S. gracilis Cox. 
. humilis Keyes. 
S.kUpparUyU^V. 
. kallanus Geinitz. 
S. \teivberrvi Stevens. 
.//««;« White. 
S.pciludinaformisli^W. 
. brevis^ White- 
S. carinatus Stevens. 
With two or three exceptions, perhaps, the other describe, 
species of the fusiform group from the American Carbonifcrou 
are apparently synonymous with one or another of those her 
enumerated. The genus probably includes besides 5. ociitii 
, Germ., Dn 
