47° 
I am indebted to Professor Eaton, for two speci- 
mens of this very interesting species. In his Geolo- 
gical Text Book, he thus describes it: “ Tail cres- 
cent-form, or concavo-convex, with the convex side 
forward, upon which the post abdomen terminates: 
abdomen contains about 12 articulatious, with an ab- 
rupt termination equal in breadth to one-fourth of 
the length of the transverse lunate tail; the articula- 
tions of the side lobes gradually incline towards the 
axis of the body, until the last pair terminate at the 
tail. Found in transition limestone at Glenn’s Falls, 
and Becroft’s mountain, near Hudson. I have a spe- 
cimen from Becroft’s mountain, with part of the 
original covering of the animal remaining.” __ 
When we first noticed the remarkable lunate ap- 
pearance of the tail of this Asaph, we supposed that 
it was occasioned by some accident, but there seems 
no doubt that this conformation is natural. In our 
specimens of this species, which are not however per- 
fect, the articulations of the abdomen do not exceed 
-8 in number. ‘The representation of this animal re- 
main given by Mr. Eaton, plate 1, figure 1, is exceed- 
ingly inaccurate; it will confuse rather than illustrate 
the subject. Our cast.and the drawing, we believe, 
are taken from the same specimen, which was kindly 
loaned by Mr. Eaton for this work. It is but jus- 
tice to the amiable, industrious, and indefatigable au- 
thor of the Geological Text Book to remark, that he 
regrets as much as any one, the insufficiency of his 
figures of the trilobites, to give any correct idea of 
the fossils they are intended to represent. 
