. . 
of 
Pare td 
‘ < 4 ; 
aT | 
Gime ii 
i ny hf 
i. i on 
Sada ih 
tf i UH 
8 31 | 
lis \ | 
i : Z\ 
} ul \ 
i 7 ee 
| OAH i 
I a i 
ea i Hind 
i inh 
ph 
| ut 4 
: ‘ Wiel 
i Mi rt i 
Pin Wek 4 
RE 
Py i | |} 
et ea 
at 4 | 
lf ay we 
¥ AE 
670 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
nence; their upper angles not truncated, or very slightly, and the superior 
faces of adjoining limbs forming almost a straight line. Radial facets 
Costals short, occupying the full width of 
the facets, subtrigonal, the upper angle obtuse. Distichals and palmars as 
long as the costals, and fully once and a half as wide as long; the lower 
rather shallow, facing upwards. 
plates of the same ray suturally connected. Arms six to the ray, exception- 
ally two or four in one of the subdivisions; they are long, cylindrical, and 
but slightly tapermg. Arm plates placed obliquely, sloping to the sides, the 
lines of union somewhat waving. Pinnules closely packed. The structure 
of the ventral disk has not been observed, being almost completely covered 
by the arms in our specimens; only portions of the middle plate of the first 
interradial row are visible, which at the four regular sides are marked by 
a conspicuous, sharply triangular convexity, while at the anal side the con- 
vexity is quadrangular, and the plate itself bulges outward, indicating the 
Stem 
distinctly elliptic, the two upper joints circular, and smaller than the dia- 
presence of some sort of protrusion in connection with the anus. 
meter of the basal rim. 
Horizon and Locality. — Kinderhook group; Le Grand, Marshall Co., 
Towa. 
Types in the collection of Wachsmuth and Springer. 
Remarks. —This form was referred by us in 1890 with considerable 
doubt to P. planus O. and Sh. More perfect specimens since obtained show 
that it differs from that species more distinctly than we had supposed, and in 
redescribing it as a new species we name it in memory of Professor Louis 
Agassiz. P. planus is a larger species than P. Agassizi, the base is conical in 
place of rounded, and it has no such rim at the lower end. This rim, which 
is represented in every specimen, is so conspicuous, and resembles so closely 
a stem joint, that we were at first inclined to regard it as such, but on grind- 
ing its surface we discovered plainly the interbasal suture lines. P. planus 
also has a greater number of arms, the arm joints are longer and about 
horizontal, while in P. Agassizi they slope at quite an angle outward. It 
differs from P. Prattent in the much smaller size of the calyx, and in having 
proportionally much longer arms, 
