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° ee. etree Pinata 
* the back are moré numerous and by no means so 
broad as those of the lateral lobes. Six costal arches 
are véry obvious on the sides, and about thirteen on 
‘the vertebral column, The lateral ribs make a very 
acute angle with those of the middle lobe, and are 
ed 
connected together in the usual manner at the terini- 
nation of the tail ; the end of the middle lobe is flat-_ 
tened and spoon-shaped. | 
This species was discovered by Mr. “Wetherill In 
the black shaly limestone of Glenn’s Falls, in the 
state of New York, which is so abundant in the 
Cryptolithus and other organic remains. After much 
trouble and research, no other specimens of this spe- 
cies could be found. Dr. J. E. Dekay, in bis valuable 
memoir on the: Jsofe/us, alludes to an Asaph found 
in this locality, good specimens of which are said to 
be in the cabinet of Major Delafield. Perhaps this 
may be the A. Micropleurus. 
As the rocks at Glenn’s Falls are very rich not 
only in trilobites, but in several other species of or- 
ganic remains, the following description of this - 
cality will perhaps not be unacceptable. 
i, Glénn’s Falls is an interesting spot not only to the 
“geologist and the naturalist, but also to the tourist in 
search of magnificent and beautiful scenery; the 
former snould visit this romantic place when the wa- 
“ter i ny the river is low, and the latter when the full 
torrent tumbles over the precipice, and dashes and i 
; which formthe bed of ® 
foams among the loose rue 
