460 
PALAEONTOLOGY OF ILLINOIS. 
FRUITS OR NUTLETS. 
Genus TRIGONOCARPUM, Brgt. 
Ill. Geol. Rep., vol. ii, p. 460. 
Trigonocarpum Ngeggerathii, LI. and Hutt. 
PI. xxxi, fig. 16. 
This fine fruit is cut in the middle by a section of a nodule which only rep¬ 
resents its internal part and structure. As the outside form is not known, 
and the internal disposition is slightly different from that of the fruit pub¬ 
lished by Lindley and Hutton, vol. ii, pi. 142, our species is doubtfully con¬ 
sidered as identical with the European one. This fruit has three distinct 
walls or envelopes. t The external one, more than one line thick, looks like a 
fleshy, soft exocarp, the part which it occupies being of the same compound as 
that of the stone, merely changed in color and intermixed with small pyrites. 
Its form is exactly ovate-pointed, slightly emarginate at the point. The second 
wall, transformed into crystallized iron, is irregular in thickness, ascends, first 
as high as the point of the central reofcletj- where it divides, one part uniting 
both borders, the other ascending near to the point where it is joined in an 
obtuse top. The third envelope, as thick as the first, ascends to the point c, 
and is a compound of a black substance mixed with fibrous tissue. The inter¬ 
nal nut is of a spongious compound like the third envelope, but is marked with 
more numerous, yellowish filaments, directed longitudinally, and irregularly 
broken across. Its point seems ascending into the first wall of the whole fruit. 
The English authors compare the fruit to that of a palm, and recognize in the 
middle of it, the place of the embryo, a depression which is not seen in ours. 
Found in a concretion of Mazon creek, by Mr. Jos. Even, to whom the spe¬ 
cimen belongs. 
Trigonocarpum olivacformis, LI. and Hutt. 
Foss. FI. 3 t. 222, fig. 1 and 3. 
Collected from the sandstone of Eugene, Ind., by Mr. John Collett. 
