312 
BULLETIN OF THE BUREAU OF FISHERIES 
Oceanic, Boreal Arctic: Rhizsolenia semispina Hensen, 7 Chaetoceras decipiens 
Cleve. 
Oceanic, Temperate: Rhizosolenia alata Brightw., R. styliformis Brightw. The 
inclusion of the following species in this group is not as yet fully established : Thal- 
assiothrix jrauenjeldii Grun. 
Oceanic, Tropical: Planktoniella sol (Brightw.) Schuett. 
In addition to the true marine planktonic diatoms the following marine, bottom, 
or semibottom (tycopelagic) diatoms (Ostenfeld., 1913) occurred abundantly at 
times: Actinoptychus undulatus (Kuetz) Ralfs., A. splendens (Bail) Ralfs., Donkinia 
recta (Donk.) Grun., Hyalodiscus stelliger Bail., Melosira sulcata (Ehr.) 8 Kutz., 
N. bombus (Ehr.) Kutz., N. cancellata Donk., N. humerosa Breb., N. smithii Breb., 
Pleurosigma affine Grun., P. fasciola (Ehr.) W. Sm. 
A few fresh-water or so-called brackish water forms were found and are here 
listed : 
Asterionella jormosa (Hass.), Bacillaria paradoxa Gmel., Campylodiscus echeneis 
Ehr., Navicula borealis (Ehr.) Kutz., Nitzschia plana W. Sm . , N. sigma (Kutz) W. Sm., 
Pleurosigma balticum W. Sm., Raphoneis amphiceros Ehr. 
Referring to the ‘above list of those neritic species of marine, planktonic diatoms 
whose distribution in other regions is well established, we find the arctic, temperate, 
and tropical groups represented in Chesapeake Bay as follows: Arctic neritic, 1; 
northerly temperate neritic, 5; southerly temperate neritic, 5; tropical neritic, 0. 
Practically all the neritic diatoms belong to the temperate group. True tropical 
neritic diatoms have not been found, and only individuals of one species ordinarily 
classed as an Arctic form have been taken. This diatom, Biddulphia aurita (Lyngb.) 
Breb. was collected once in Chesapeake Bay during March, 1916, at area A in a sur- 
face sample. It was found to be common, according to Mann (1894), in deep-water 
dredgings off the mouth of Delaware Bay; it has occurred as an occasional species 
in Massachusetts Bay (April, 1913) according to Bigelow, and was common through- 
out most of the year 1916 (possibly 1915) in the Bay of Fundy according to Bailey 
(1917). Gran (1919) has found it a little farther north in the Gulf of St. Lawrence, 
and finally Cleve (1897) mentions it as occurring rarely in a few samples in Baffins 
Bay and Davis Straits. 
The oceanic diatoms are distributed in regard to number of species in the different 
geographic groups as follows: Boreal, arctic oceanic, 2; temperate oceanic, 2; and 
tropical oceanic, 1. 
Albert Mann (1894) has studied the diatoms dredged by the U. S. S. Albatross 
in 813 fathoms (1,487 meters) of water off the mouth of Delaware Bay, and has found 
a large number of species many of which are fresh-water forms characteristic of rivers 
in that latitude. He believes that they have been supplied largely by the Delaware 
River. In addition to these fresh-water forms, however, there are many marine 
for ms , a few of which, as Mann says, may have been deposited there by the Gulf 
Stream. Those diatoms common to both regions are the following: Navicula borealis 
Ehrb., Raphoneis amphiceros E., Actinoptychus undulatus Ehrb., A. splendens Ralfs., 
Melosira sulcata Kz., Navicula humerosa Breb., N. smithii Breb., Pleurosigma aifine 
Grun., Biddulphia aurita Lyngb., Ditylum brightwellii West., and Rhizosolenia 
stylijormis Bright. 
7 Rhizosolenia hebetata oar. ’semispina JJle.nsevd. 
» Paralia sulcata (Ehr.). 
