TISSOTIID ®. 53 
The remaining lateral lobes are like those of the same species, but 
very much narrower, and the second to the fifth hardly more than mere 
indentations. 
The dorsal sutures were seen only from above. The antisiphonal 
lobe was obviously very narrow at the base, but its length could not be 
determined. There are seven pairs of entire zygous dorsal lobes and 
saddles, the latter much narrower than the external laterals. The first and 
second lateral saddles are connected across the septum by broad ridges, so 
that the septum observed was convex externally and internally along the 
mesal plane, but concave along the center. The saddles on the dorsum 
and the corresponding external saddles were connected only by very 
slight ridges, and the intermediate surface of the septum was convex. 
The figures of sections show the broad globose, keelless form of the 
hepionic stages and perhaps of the earliest of the neanic stages. The 
siphunele is certainly véry small and the keel is solid when it first appears, 
as shown in figure. The disappearance of the siphuncle left me in doubt 
with reference to its structure in later stages. 
Locality: Cachiyacu, west side of Huallagua River, Peru. 
Age: Upper Cretaceous, probably Senonian. 
PARATISSOTIA REGULARIS n. sp. Hyatt. 
Pl. IIL, figs. 1-6. 
Buchiceras serratum Hyatt (pars), 1875, Proc. Boston Soc. Nat. Hist., Vol. XVII, 
p- 370. 
This species has a broad volution with a rounded venter until the shell 
reaches a diameter of 6 mm. <A broad, low keel next makes its appearance 
and the next volution becomes helmet-shaped in section. There is cer- 
tainly one line of nodes on the umbilical shoulders at this time, and the 
umbilical zone is broad and at an angle of about 45° with the line of 
involution. This helmet-shaped section, with more or less gibbous sides. 
is retained through life, but becomes more compressed; the keel becomes 
subacute and prominent, and slight concave zones appear on either side of 
it. An outer line of tubercles appears on the edges of the elevated venter, 
and both lines increase steadily in size. The umbilical zone becomes 
rounded and is in the first ephebic substage at mght angles to the plane of 
coiling. The two lines of tubercles are connected in the ephebic stage, 
