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