503 
PALAEONTOLOGY OF NEW YORK. 
Graptolithus logani. 
Frond composed of numerous branches nearly equally disposed on two 
sides of a central connecting stipe, and each again subdividing nearly 
equally; after which they bifurcate, always near the base, with greater 
or less regularity : connecting membrane thin, composed of the same 
substance and continuous with the branches, extending from the centre 
to some distance beyond the bifurcations. The branches, after the third 
bifurcation, become marked on the inner side by a row of cellules, and 
along the centre by an abruptly impressed line which follows the di¬ 
varication of the branches : cellules minute, not prominent towards the 
base of the branches, being compressed vertically, and appearing like a 
double series with a central depressed line, becoming developed as they 
recede from the base. The branches beyond the disc are turned on one 
