BIOLOGICAL STUDY OF CHESAPEAKE BAY WATERS 
311 
in the early spring and that the maximum bottom temperature is attained at times in 
the late summer and at times in the autumn. 
BACILLARIOPHYTA 
DIATOMS 
The ^identifications of the diatoms found in the plankton of Chesapeake Bay 
have been made by Dr. J. J. Wolfe, and the original list may be found in a paper by 
Wolfe and Cunningham (1926). A considerable number of bottom diatoms stirred 
up by currents and semibottom diatoms are included. The discussion which follows 
is based on data tabulated by Doctor Cunningham. 
GEOGRAPHICAL DISTRIBUTION 
An examination of the list of diatoms with reference to the recorded distribution 
in other parts of the world shows that the various species mentioned may be classed 
as fresh water, brackish water, and marine diatoms. It is evident, judging from what 
is known of the distribution of marine diatoms in other regions, that those found in the 
bay include some neritic species (bottom or semibottom forms) which are not placed 
among the true planktonic forms, some which are considered to be true planktonic forms 
inhabiting coastal regions (neritic), and still others, also planktonic, which are spoken 
of as oceanic forms since they are ordinarily found outside of the coastal regions in 
the great ocean currents where the salinity is high. Furthermore, a glance at the list 
of neritic and oceanic species of diatoms shows that if we follow Cleve’s (1897, 1901-02) 
grouping into arctic, temperate, and tropical forms all three groups are represented in 
Chesapeake Bay, although naturally the temperate forms are much in excess of the 
others. The grouping in the list given below is based on that of Cleve, but it has 
been modified to some extent in the light of the more recent work of Gran, Osten- 
feld, Lemmermann, Karsten, Johnstone, Bigelow, and Fish. Unfortunately, our 
knowledge of the distribution of the various species of diatoms, even in the Atlantic 
Ocean, is still imperfect and the different groupings overlap one another to a con- 
siderable extent, so that the distribution given must be looked upon as tentative. 
The following marine planktonic diatoms have been found in Chesapeake Bay. 
Species of Coscinodiscus and other species, concerning which there is confusion as to 
identification, have been left out. Those listed have been arranged according to their 
usually accepted distribution with reference to the arctic, temperate, and tropical 
regions of the Atlantic Ocean. 
Neritic, Arctic: Biddulphia aurita (Lyngb.) Breb. 
Neritic, Northerly Temperate: Chaetoceras teres CL, Leptocylindrus danicus CL, 
Rhizosolenia setigera Brightw., Skeletonema costatum (Grev.), Thalassiothrix nitz- 
schioides Grun. Another form which may be included in this group but whose posi- 
tion is somewhat uncertain is Nitzschia longissima (Breb.) Ralfs. 
Neritic, Southerly Temperate: Biddulphia mobiliensis (Bail), Cerataulina 
bergonii Perag., Ditylium brightwellii (West) Grun., Eucampia zodiacus Ehr., Guin- 
ardia flaccida (Castrac.) Perag. The following may be placed in this group, but 
their distribution is still uncertain : Bacteriastrum varians Lauder, Bellerochea malleus 
(Brightw.), Lithodesmium undulatum Ehr., Rhizosolenia calcar avis Schultze, Rhizo- 
solenia stolterjothii Perag. 
Neritic, Tropical: None. 
