LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

DESCRIPTION OF SPECIES 209
descendants, although certain smaller forms included in this family appear in later
Aptian time, including two or more species of Hamilictrat n. gen.
Little has been found in the literature bearing upon the life history or habits of
AncyloceTat species. Judging from their protective armament, especially about the
body-chambcr, it may be inferred tbat in this basin they had powerful adversaries
and that these may have been the cause of their short career in these waters. Most
of the shells found here bear evidence of battle and of death from injury, especially
evident in the crushing of the shaft or septate part of the cone. In many eases the
shaft is crushed immediately beneath the body-chamber, leaving other parts still
entire. Possibly such injuries were inflicted by other cephalopod forma having no
shell. That at least some species of Ancyloceras were carnivorous, preying upon
weaker members of their claos, is indicated in an example of Ancylocerat at IT ox nov.,
the lower part of whose body-chamber was found, showing clearly that immediately
above the last septum, in the space presumably occupied by the stomach of tho
animal, the shell was filled with fragmented shells of other smaller species of cephalopoda.
In one example of Tropaeum percattatum a number of small belemnoids were
found at the aperture, in such position as to indicate that they bad been taken by it
Similar facts were observed in an example of Lytocerai aulaeum, wherein belemnoids
and other small molluscan species were found similarly situated.
Ancyloceras thphas Anderson, n. sp.
[Ptal« M. Ggtua I, 3: plsta SB, Sture 1
Shell large, robust, coiling ancyloeeratid, closely costate, costae changing with
growth; earlier coils trituberculate; shaft with close-set nearly straight, rounded
ribs encircling it, at first normal to the dorsal border; later becoming oblique,
especially on the body-chamber; each fifth or sixth rib trituberculate; the tuberculcs
on the younger whorls small, mammillary; on the older part at first low
and tumid, confined to the two inner (dorsal) rows, and on the body chamber becoming
prominent and spinose in three outer rows; body-chamber broadly inflated, especially
below the bend, but near the aperture the section becomes narrowed to a slotlike
opening about one-fourth the width of the body-chamber; recurved portion of
the ahell bearing thick and nearly straight ribs, surmounted by broad, strong spines J
section of recurved limb quadrate, higher than broad. Tho species belongs to the
group of A. retwiiiianum d'Orbigny, having a similar form and protective equipment.
The major ribs and spines develop from the point where septation ends and
increase in strength and prominence with the further growth of the body chamber.
The holotype (Calif. Acad. Sci. type Coll.) was found in the Mitchell zone, near
Roaring River, & miles south of Ono, Shasta County, asaociated with ShasiicrioctTaji
pomente, Inctxramus evataiden, and ether cephalopoda. The holotype has the following
dimensions, total length, 10 inches; the shaft, somewhat elliptical in section,
increases in greater diameter from 2.6 to 4.5 inches near the last septum, where the
greater axis changes from a dorse-ventral to a tranaverse direction. The greatest
width of the shell is near the middle of the body-chamber, where the transverse width
is nearly 5 inches. The horizon of this speciea is thought to be near the upper limit
of the Barremian. The shaft of the holotype is crushed beneath the body-chamber.
Only fragments of other examples of the specics have been found.
A ncyjacmw aUrax Anderson, n. sp.
(PM( St, 6*ura I, I, 3, 3d)
Shell large, robust, coiling ancyloceratid, heavily costate, trituberculate, having
major and minor ribs; major ribs tuberculate, with one or two mi nor unadorned
ribs intervening between them; ornamentation of shaft and younger coiled portions