565 
upon the edge of the aperture or rather in the base of the dorsal 
crest. The aperture had the usual shelf-like constriction figured 
by Meek and on the dorsal side were two narrow sinuses and a 
median dorsal crest, the length of which could not be determined. 
Mr. Stanton, in his ‘‘ Colorado Formation,’’* shows a similar re- 
tention of the impressed zone in Scaphites ventricosus. 
The gerontic whorl is quite free for some distance, and although 
the impressed zone sensibly diminishes in depth and_ breadth 
towards the aperture it is not obliterated. These two species have 
comparatively short living chambers, which are free only for a part 
of their length, and one would naturally expect that the very deep 
contact furrow of the ephebic and anagerontic substage would per- 
sist. The conditions are quite different from those that occur in 
shells with more extended gerontic stages, like Scaphites larve- 
Jormis, Meek and Hayden, and in these the paragerontic substage 
may perhaps have no impressed zone. 
I have, however, examined a considerable number of scaphitoid 
sheils from European localities and some of these gave positive 
information of the persistence of the impressed zone in the lower, 
inner border of the aperture, although, as in Scaphites nodosus, it 
was sometimes hardly perceptible in the outline of this part. 
Felicancylide. 
This family name serves the purpose of temporarily uniting all 
phylogerontic species of the Cretaceous in America which have 
three rows of tubercles on either side. The characteristics are 
given below under the generic title ‘* Helicancylus.”’ 
LFelicancylus, Gabb.t 
It is probable that genetic connection as shown by the ornamen- 
tation existed between cretacic shells of normal involute form like 
Acanthoceras Rémondi of the nodose variety figured by Gabb as 
having three rows of tubercles and his Crzoceras latus.{ This last 
also has three rows of spines and single costze, but has an open coil 
without an impressed zone. ‘There are similar marks of affinity in 
the species described by the same author as Helicancylus equicosta- 
zus, which has also three rows of nodes. ‘The last, however, has the 
* Bull. U.S. Geol. Survey, Pls. xliv and xly. 
+ Pal. Cal., i, Pl. xiii, and ii, Pl. xxv. 
HIG iPlay, bis. 2. 
