174 Hall on the 



is offered of examining the ^erratures. It seems quite probable 

 that this may prove a distinct species. 



A single fragment of a ramose form, with two branches like G% 

 ramosus, of New York, has been observed, but I have not thought 

 it desirable to give its characters at present. 



Among other forms of the Graptolitidece, there are at least three 

 species of Dictyonema, which are of common occurrence, associ- 

 ated with the Graptolites of Point Levy. 



The genus Dictyonema was described in the Palaeontology of 

 New York, vol. 2, p. 174, from an examination of the broad fia- 

 belliform or sub-circular expansions of corneous reticulated fronds 

 common in the shales of the Niagara group. These forms were 

 described as having " the appearance and texture of Graptolites, 

 to which they were doubtless closely allied," Further examina- 

 tions have demonstrated the truth of this remark in the discovery 

 of serratures, like those of Graptolithus, on the inner side of the 

 branchlets of both D. retiformis and D. gracilis. The celluli- 

 ferons side adhering more closely to the stone than the opposite, 

 as in Ratepora and Fenestella, is much more rarely seen than the 

 other. The mode of growth, though probably flabelliform in some 

 species, is clearly funnel shaped in D. retiformis, the serratures 

 being upon the inner side as in Fenestella. 



The generic characters heretofore given may therefore be ex- 

 tended as follows. 



DICTYONEMA. 



Generic characters. — Frond consisting of flabelliform or funnel- 

 shaped expansions, (circular from compression) composed of 

 slender radiating branches, which frequently bifurcate as they re- 

 cede from the base ; branches and subdivisions united laterally by 

 fine transverse dissepiments ; exterior of branches strongly striated 

 and often deeply indented ; inner surface celluliferous or serrate, 

 as in Graptolithus* 



The general aspect of the species of this genus is like that of 

 Fenestella, both in the form of the fronds and the bifurcation of the 



* A paper by J. W. Salter, Esq., Paloeontologist of the Geological 

 Survey of Great Britain, read before the American Association, for the 

 advancement of Science, at the Montreal Meeting, 1857, describes a new 

 genus of the Graptolite family under the name of Graptopora. Although 

 having had no opportunity of examining this paper, it appears to me 

 that the forms described are true Dictyonema. 



