43 
Seneca, Ontario County, New York, in dark, slaty 
limestone, which also contains cubical crystals of 
iron pyrites. A fortunate blow of the hammer has 
fractured the rock which contains this trilobite, so 
neatly, as to present us at the same time with the 
petrified animal in an almost perfect state, and also 
with the mould or matrix in which it was imbedded. 
This arrangement is Begntitaliny! apetraned by our 
- models. 7 
Genus Asapuus. Brongniart. 
This genus derives its name from the Greek word 
Aca?ms—obscure. It embraces perhaps more species 
than any other genus of the family of trilobites. 
About twenty have already been discovered. Most 
of them are very characteristic and can easily be de- 
termined, but as the genus Asaphus, is intermediate 
between Calymene and Ogygia, it-1s sometimes a 
little difficult to decide the genus to which the inos- 
culating species on each side, belongs. 
In general, the Asaphs may be known by the body 
being very much depressed, and by the membranaceous 
development, which extends beyond the lateral lobes. 
The middle lobe of the abdomen, is rarely more 
than one-fifth the width of the body. As the abdo- 
-men and tail of the Asaph are the only portions of 
the animal commonly found entire, the distinctive 
characters of the genus above given, may Noone 
be ascertained. 7 oe 
Professor Brongniart remarks, that the ribs of the 
- Asaph, which correspond in number and positign to 
