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BULLETIN OF THE BUREAU OF FISHERIES 
group but which is sometimes included among the neritic tropical forms, does not 
seem to have been taken at all by Bailey, Fritz, Gran, Mann, or Cleve in more northern 
waters. It occurred in fairly large numbers in Chesapeake Bay during the year 1916 
and was widely distributed over the bay. At area A, near the mouth of the bay, it 
was taken on the cruises of October, 1915, January, March, April, June, July, and 
September, 1916; in other words during all the cruises except December, 1915. Far- 
ther up the bay it was recorded also during December. The highest counts were 
obtained during the April cruise and the smallest during the July cruise. The two 
largest counts were those of area J, 6,400 at 27 meters (estimated at 18.00 per mille, 
8.8° C.), and of area L, 6,500 at 26 meters (17.63 per mille, 8.9° C.), during the April 
cruise. It will be noted that both areas mentioned are close to the mouth of the 
Potomac River. This form was found as far north as area X on the cruises of Decem- 
ber, 1915, January, March, and September, 1916, when the salinity was comparatively 
high for that region. During the January cruise the surface count was 100 (11.13 
per mille, 1.0° C.), and that at 28 meters, 3,000 (17.00 per mille, 3.6° C.). The wide 
distribution of this diatom in Chesapeake Bay, its occurrence there during a large 
part of the year, and the fairly large numbers during the spring maximum in the 
region of the mouth of the Potomac River are conditions which favor its inclusion 
under the neritic group, where Cleve, Ostenfeld, and Fish have placed it, rather than 
under the oceanic group to which it has been assigned by Gran (1908). 
Rhizosolenia stolterfothii was found as far north as area X, in very small numbers 
on the cruise of June, 1916. During the winter cruises (December, 1915, January, 
1916) and even on the March cruise this form was almost absent from the plankton; 
but in April it was very abundant at two areas under the following conditions : Area 
6, surface 126,000 (21.92 per mille, 11.1° C.), 18 meters 52,000 (29.78 per mille, 
7.0° C.); area P, surface 49,800 (11.98 per mille, 10.3° C.), 11 meters 11,400 (12.12 
per mille, 10.6° C.). At other areas there were no records of its occurrence in 
April. During the summer cruises (June and July) the counts were small, but in 
September large numbers were found at area F, surface 35,900 (27.54 per mille, 
22.5° C.) and area A, surface 79,000 (23.59 per mille, 23.4° C.). This species was 
evidently widely distributed over the bay but in small numbers except in the lower 
half, where it was most abundant near the mouth (areas A, F, G ). As in the case of 
Skeletonema costatum, the largest counts were obtained at 27 meters for area A, at 9 
meters for area L and at the surface for area R during the October cruise of 1915. 
The records for the remaining diatoms included in the neritic southerly temperate 
group indicate that they did not flourish in Chesapeake Bay, at least during the year 
1916, that they occurred in largest numbers near the mouth of the bay, and that the 
counts near the mouth of the Potomac River were not conspicuously large. There 
is some indication that Guinardia jlaccida (Castrac.) Perg., Biddulphia mobiliensis 
(Bail.), and Bellerochea malleus (Brightw.) have maxima in the autumn and the 
spring. The data for Ditylium brightwellii (West) Grun., Eucampia zodiacus Ehr., 
Lithodesmium undulatum Ehr., and Bacteriastrum varians Lauder are so meager that 
it is unjustifiable to discuss them in detail. 
No neritic tropical forms were found in Chesapeake Bay unless Bellerochea malleus 
and Rhizosolenia calcar avis, which I have included provisionally in the neritic south 
temperate group, are considered as tropical forms. 
The oceanic diatoms were not abundantly represented in Chesapeake Bay during 
1916 — a condition which should be expected, since pure oceanic water, so far as our 
