174 
PALAEONTOLOGY OF NEW-YORIC. 
The following species present no positive characters by which they can be identified either 
as bryozoa or true corals, except in their mode of growth and general appearance. They have 
usually been referred to Gorgonia, but there are really no characters visible by which such 
reference can be made. 
Genus DICTYONEMA ( nov . gen .). 
[Gr. Sixnov, rete, and vs^u, filum .] 
Frond circular or flabelliform, composed of slender radiating branches which frequently 
bifurcate as they extend towards the margin ; branches and subdivisions united laterally by fine 
transverse dissepiments ; branches impressed with deep striae or grooves, producing indentations 
that sometimes have an elongated rhomboidal form ; axis subcalcareous with a corneous exterior. 
The general structure of this coral is very similar to Fenestella, in its diverging bifurcating 
branches with transverse dissepiments. The branches appear like flattened black threads united 
laterally by finer ones, leaving quadrangular interstices. One species forms large circular fronds 
sometimes a foot in diameter, while the other has been seen only in flabellate forms. The 
branches of these corals consist of a black film enveloping a semi-calcareous or corneous in¬ 
terior, and they have the appearance and texture of Graptolites, to which they are doubtless 
closely allied. A single branch, where the lateral connexion with others is broken off, can 
scarcely be distinguished from some species of Graptolites. 
569. 1. DICTYONEMA RETIFORMIS ( n . sp .). 
Pl. XL F. Fig. 1 a, b. 
Gorgonia1 retiformis. Geol. Rep. 4th District, p. 115, tig. 1, 1843. 
Frond circular, or expanded cyathiform in its growing state (flattened in its fossil condition) ; 
branches thin, flat, frequently bifurcating, united laterally by obliquely transverse filaments, 
leaving oblong quadrangular interstices ; surfaces of branches indented, or intermittingly striated 
in an oblique direction. 
This species is readily recognized in its more perfect condition by the circular form, compa¬ 
ratively broad and flattened branches, which radiate on every side from a centre. The branches 
do not strictly reticulate, although a cursory examination gives this impression, particularly in 
fragments where the circular character of the frond and radiating branches are not observable. 
It is a common species in the shale at Lockport, and fragments are found at nearly all localities 
of the same rock, though perfect fronds are extremely rare. 
The species can have very little if any true relations with Gorgonia, to which it was 
previously referred, with doubt, upon the authority of Lonsdale’s figures in Murchison’s Si¬ 
lurian System. The specimens are preserved in calcareous shale, where the most minute and 
delicate forms of Fenestella and Retepora retain their texture in the most perfect manner. 
