52 



[Assembly 



The forms above described do not by any means exhaust the va- 

 riety presented in this collection. With a single exception, however, 

 all the specimens which offer any new light in regard to the habit 

 of the Graptolites indicate that the mode of growth was in the 

 manner described, in branches radiating from a centre, or in tufts 

 joining in a central connecting substance. 



The specimens from the Canadian locality afford further evidence 

 in confirmation of what we have elsewhere observed, that, with few 

 exceptions, the species have a limited geographical range. This 

 locality has already, after very cursory examination, afforded eight 

 new species of Graptolites, with one or two species which appear to 

 be identical with those previously found in the State of New- York. 

 A comparison of specimens from more southern localities, with those 

 of New-York, shows a large proportion of new species; and it now 

 appears probable that the number of American species of Graptolithus 

 previously known (about twenty), will soon be increased by an 

 equal number of new ones. 



Locality and formation. Point Levy : Hudson-river group. 



In addition to the species above noticed, the following are pu- 

 blished in the same Report for 1857 : 



Graptolithus Jlexilis, 



G. 



rigidus, 



G. 



nitidus, 



G. 



octohrachiatus, 



G. 



hifidus, 



G. 



octonarius, 



G. 



patulus, 



G. 



quadrihrachiatus, 



G. 



extensus, 



G. 



crucifer, 



G. 



denticulatus, 



G. 



bryonoides, 



G. 



pristiniformis, 



G. 



headi, 



G. 



ensiformis, and 



G. 



alatus^ 



G. 



tentaculatus. 



G. 



fruticosus, 



Graptolithus indentus, 



Besides these species of Graptolithus, there are some other forms 

 separated by the writer under the name Phyllograptus, as follows : 



Genus Phyllograptus. 



Frond consisting of simple foliate expansions, celluliferous or serrated 

 upon the two opposite sides : margins with a mucronate extension from 

 each cellule ; or of similar foliate forms united rectangularly by their 

 longitudinal axes, and furnished on their outer margins with similar 

 cellules or serratures, the whole supported on a slender radicle. 



