546 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
(?) Megistocrinus abnormis (Lyoy). 
Late AolieNs igs. Tab, 
1857. Actinocrinus abnormis — Lyon ; Geol. Rep. Ky., Vol. IIL., p- 479, Plate 4, Figs. 1, 1a, 6. 
1865. Megistocrinus abnormis — SHuMaARD; Catal. Paleoz. Foss. N. Amer., p. 380. 
1881. Megistocrinus abnormis — W. and Sv.; Revision Paleocr., Part IIL., p. 137. 
This species is remarkable for the large lobes at the arm regions, which 
give to the calyx a distinctly pentalobate outline, with deep interradial 
notches. Dorsal cup saucer-shaped, a little flattened at the bottom; the 
plates thin, flat or slightly concave, and devoid of ornamentation. 
Basals in the same plane with the radials, forming a flat hexagonal disk, 
of which only a narrow margin is visible beyond the column; central canal 
large and obtusely pentangular. Radials and costals nearly of equal. size. 
Distichals 3X 2 in the two antero-lateral rays, supporting the arms; the 
three other rays have an axillary in each division and 2 X 4 palmars. Prim- 
ary arms sixteen; arranged: 4%. Interbrachials: 1, 2, 3, 3, 3; the first as 
large as the radials; those of the second row about the same size as the 
distichals; the plates of the third row considerably smaller; the middle 
pieces of the fourth row often located in the tegmen. Interdistichals one or 
two; there are generally two in rays with four arms, and the lower one 
rests upon the truncated middle part of the preceding axillary, but where 
there is but one it occupies the notch between the first distichals. Anal 
interradius extremely wide and somewhat flattened ; the first anal, which ‘is 
fully as large as the radials, often supports four plates in the first row, and 
five to seven in the second and third. Tegmen highly convex, composed of 
medium sized, irregular, flat pieces, the ambulacra marked by ridges, and 
the interambulacral spaces by depressions. Orals in contact; the posterior 
one and the radial dome plates strongly tuberculous or subspinous, forming 
SIX conspicuous prominences upon the surface. Anus located a little above 
the arm bases, opening out through the flat surface of the tegmen. 
Horizon and Locality. — Corniferous; Louisville, Ky., Clarke Co., Ind., - 
and Marian Co., Ky. Very abundant in some localities, but good specimens 
quite rare. 
Types in the Lyon collection. 
Remarks. — This is not a typical Megistocrinus, and we have referred it 
with much hesitation to that genus. It departs from the typical form in the 
wide and deep depressions at the arm regions, in the flattening of the anal 
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