Edwards, on Diatomacecs. 
87 
Actinocyclus undulatus. 
Tryblioiiella punctata. 
Dorypliora ampbiceros. 
Grammatophora serpentina. 
„ macilenta. 
„ marina. 
„ stricta. 
Campylodiscus Hodgsonii. 
Stauroneis pulchella. 
Coscinodiscus subtiiis. 
„ oculus-iridis. 
„ eccentricus. 
„ radiatus. 
Biddulphia aurita. 
Pinnularia distans. 
Pleurcsigma strigosum. 
„ fasciola. 
Navicula ovalis. 
„ didjma. 
Cocconeis scutellura. 
Hhabdouema arcuatum. 
„ minutum. 
Triceratium alternans. 
Orthosira marina. 
Synedra salina. 
Surirelia gemma. 
HURL-GAT. 
At a place wliicli, from its numerous reefs, whirlpools, and 
dangerous passages, was called by the Dutch settlers of New 
York City, Hurl-gat,^^ or, as it is now commonly termed. 
Hell-gate, on the rocks and algse, which are very plentiful, 
a large quantity of Diatomacese were found growing. Hurl- 
gat is in the Long Island Sound and close to New York City. 
The following species were found : 
Biddulphia Isevis. Synedra radians. 
„ pulchella. „ affinis, 
„ reticulata ? Rhipidophora elongata. 
Cocconeis scutellum. Schizonema Grevillii. 
Coscinodiscus oculus-iridis. „ Smithii. 
„ eccentricus. „ cruciger. 
„ radiatus. Podocystis americana. 
„ subtiiis. Gomphonema marina. 
Actinoptychus. Homoeocladia filiformis. 
Rhabdonema arcuatum. Podosphsenia Lyngbyei. 
„ adriaticum. „ Elirenbergii. 
Grammatophora marina. Nitzschia angularis. 
Synedra tabulata. Melosira Borreri. 
The Actinoptychus here set down belongs to the group of 
which Smithes Eupodiscus fulvus and crassus are members, 
all of which, in my opinion, belong to the genus Coscino- 
discus. The obscurity which seems to hang over several of 
the discoid Diatomacese in the minds of many microscopists 
could not exist if they had carefully studied the works of 
Ehrenberg, and examined the living frustules. The con- 
fusion that seems to exist between the genera Coscinodiscus y 
Actinophcenia, Actinoptychus, and Actinocyclus is very great ; 
and, to aid towards its clearing up, I give my opinion on the 
subject, resulting from the careful examination of many spe- 
cimens. 
The genus Actinocyclus has but two representatives, one of 
which has the segments situated on different planes, and is 
