40 Description of a New Trilobite. 
Art. IlI.—Description of a New Trilobite ; by Jacop Green, — 
M. D, Prof. of Chemistry in the Yeiérson Medical College, 
Philadelphia. 
Asaphus Diurus—GRreen. 
Girne? costis striatis, tubereulatis ; cauda bipartita; corpore 
depresso. 
The fragments of this Asaph which I have examined, consist 
of nineteen articulations of the abdomen and tail. The costal 
arches of the lateral lobes are very peculiar. 'They are marked 
by a shallow groove, or impressed: line on their upper surface, 
studded on each side with quite a regular row of bead-like granu- 
lations. On each division of the vertebral column, there is buta 
single row of pustulations. The lunate caudal end is more ex- 
panded than in the cognate species, the A. Selenurus, and the 
concave side of the cressent, is more regularly rounded; the 
whole animal is much more depressed, than that species, and 
the lateral lobes are much wider in proportion to the middle lobe 
of the back. 
There are two specimens of this fine species in the cabinet of 
William Wagner, Esq., of Philadelphia, both of which were found 
in Green County, Ohio, in the neighborhood of Xenia. The 
largest which measures two inches long and two and a half inches 
wide, is a plaster cast from a weather beaten natural mould; the 
other occurs in a grey, sparry, argillaceous limestone rock. It is. 
perhaps worthy of remark, that all the specimens of the Asaph, 
with a lunate tail which I have noticed, were natural moulds, 
made by the animal in the rock, the shell or body having disap- 
peared. 
I was informed some time since, by Mr. Abraham Sager, of 
New York, that he had discovered several fine specimens of a0 
Asaph with a lunate tail at the foot of the Helderberg mountains 
near the Caves, in which the horns of crescent which forms the 
caudal termination were remarkably elongated and perfect. AS 
the A, Selenurus is found at Glenn’s falls and at Becroft’s mout- 
tain near the city of Hudson, is quite a different rock from that 
which occurs at the Helderberg, and as this last formation seems 
analogous to the one in which the Asaphus Diurus is found, it is 
probable that Mr. Sager’s species may be the one now described: 
I am indebted to the kindness of Mr. Wagner, for the opportu- 
nity of making out this species. 
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