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Phymotaxis
mansfieldi Cooke
Plate 6,
figures 4-8
Phymotaxis
mansfieldi Cooke, 1941, Journ. Paleaontology, v. 15 no. 1, p. 18,
pl. 4, figs. 6-8.
Test large, subhemispherical, with evenly rounded margin, slightly
concave near the peristome. Apical system unknown. Ambulacra about
half as wide as the interambulacra ; poriferous zones forming single
arcs of about eight zygorpores above the ambuitus, zygopores
irregularly distributed in a broader zone below the ambitus. Tubercles
large, imperforate, two rows on each ambulacrum, four rows on each
interamb ulacrum at the ambitus, the lateral rows not extending to the
apex ; each primary tubercle surrounded by a row of little tubercles
that generally follow the edges of the plate, one little tubercle at
each angle of the plate being somewhat larger than the others.
Peristome rather small, subdecagonal ; gill slits moderately deep,
callous.
Horizontal diameter of largest cotype 56 mm. ; height 27 mm. ; diamter
of peristome 20 mm.
Occurence.
- Florida : Old quarry of Florida Rock Products Company 3/4 mile
southwest of Brooksville (USGS 12755, W. C. Mansfield and G. M.
Ponton). Consolidated Rock Products Company 3 miles northeast of
Brooksville (USGS 12321, W. D. Mansfield and F. S. MacNeil). |
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Geologic unit. - Late Oligocene, Suwannee limestone.
Types. - USNM 372868, two nearly complete individuals and one
smaller fragment.
Comparison. - No other American species of Phymotaxis
are known. Phymotaxis mansfieldi differs from P. tournouri
of Cretaceous age as figured by Cotteau in the less plainly biserial
arrangement of the zygopores on the under surface and in the more
conspicuous arcuate arrangement on the upper surface. In theses
respects it is more nearly similar to P. biarritzensis of
Eocene age (Cotteau, 1892, pl. 322, figs. 5-7) and P. vidali (Cotteau,
1892, pl. 322, fig. 8 ; pl. 323), but its gill slits are deeper and
sharper.
Planche 6 (extrait)
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