15. 
] from 
‘ations 
The.abdomen and fail cannot be distinguish 
each other. There are seventeen distinct artic 
in both. The middle lobe is very convex, and is sep- 
arate:l from the lateral ones, by a deep channel, it 
gradually tapers to an obtuse tip. In our specimen 
there is a small part of the tail of another trilobite 
deposited in this place, which at first sight appears to 
be a dislocated fragment of our animal. 
The /aferal lobes are flattened ; the costa 
are very distinct near their insertion, and for about 
half their length, but towards their free extremities 
they are a good deal obliterated. ‘There appears to 
arches 
have been a delicate membranaceous prolongation for 
a considerable distance beyond the solid portion of 
each rib. This organization is very apparent on the 
costal arches of the tail. ‘Thereisa deep groove run- 
ning obliquely over the upper surface of each rib. 
Length of the fossil about nine inches ; bréadth about 
four inches. 
This remarkat. species of tribolite I have named 
in compliment to our zealous: naturalist, Ricuarp 
Harzan, M. D., who sent me the specimen above de- 
scribed, with the following note. — | 
Dear Sir,—During my recent visit to Boston, I 
observed the fine specimen of trilobite which accom- 
panies this note, in the cabinet of Mr. Francis At- 
GER, to whose politeness I owe this. opportunity of of- 
fering you an. additional species for your interesting 
