: 10 
42. Eucampia zodiacus Ehr.—Hab. Dredged by Mr. Powel, off rock at 
Newport, R. I. Rare. 
43. Rhabdonema minutum Kiitzing.—Hab. Narragansett rock, on alge. 
Newport harbor, on alge, Mr. Powel. Stonington rocks, on alge. 
44, Cymbosira Agardhii Kiitzing.—Hab. Rock off New Rochelle. Ston- 
ington Inlet. 
45. Tessella interrupta Kiitzing.—Hab. Off rocks at New Rochelle, on 
alge. 
46. Amphitetras antediluviana Khr.—Hab. Mud from Black Rock 
Harbor, along with Var. 8. On alge from New Rochelle. Mud from St. Mary’s 
river. Rice field, Savannah, mud. 
47. Biddulphia t ur gida.—AHab. St. Mary’s river, on alge. St. Augustine’s 
Quay, Florida. 
48. Isthmia nervosa Kiitzing.—Hab. Riviere du Loup, St. Lawrence river‘ 
onalge. L. I. Sound, fragments. Very rare. 
49. Bacteriastrum furcatum Shadbolt.—Hab. Mud from St. Mary’s river, 
Ga., also on alge. St. Sebastian’s river, on alge. Fernandina, Florida. Rice 
field mud, Savannah river. 
Var. 8.—Without the bifurcate arrangement at the extremities. 
50. Bacteriastrum curvatum Shadbolt.—Habh. Same localities as above. 
Detected by Mr. Febiger in some mud brought by me from St. Mary’s river, 
marsh. ° 
51. Asterionella Bleakleyi W. Smith.—Hab. St. Mary’s river, on alge. 
Fernandina wharf. Ogeechee canal. Savannah rice field mud, Savannah. 
This species occurs in greatest abundance at St. Mary’s, Ga. It differs slightly 
from the specimens figured in Mic. Journ., in the outline of the valve, 
which is more slender in the American variety, and also less inflated at the 
base. I am of opinion that the normal number of frustules is four, which 
may be increased to eight by subdivision, but in this latter case the persist- 
ence of these is of short duration, two separate aggregations of four each re- 
sulting, this being the largest number capable of cohering perfectly. A group 
of four individuals undergoing subdivision is shown in P]. II. f. 9, from rice field 
mud. It may here be mentioned that Asterionella formosa and A. Ralfsii? 
are occasionally met with in fresh water localities in this country. At a pond 
on Longacoming, N. J., Mr. Powel made a gathering, containing both these 
forms, along with a third, which differs so entirely from the described species, 
as to entitle it to rank as a distinct one. The valves are only about three 
times as long as broad, somewhat contracted in the centre. The striew are 
indeterminate. Asterionella formosa occurs in the Delaware river, blue 
clay; also in mud from Cooper’s creek. Diatoma stellaris of Bailey, 
is no doubt referable to this genus. 
52. Plagiogramma Gre gorianum (Greville.—Hab. Entire Atlantic coast, 
L. I. Sound. At Black Rock Harbor, in mud and on alge. New London mud. 
New Haven, Conn. Chesapeake Bay oysters. Rice field mud, Savannah. 
Never in great quantity. 
The frustules of this somewhat doubtful genus vary very much in outline 
and the vittze are often absent. 
53. Plagiogramma tesselatum Greville-—Hab. Black Rock Harbor, in 
mud. Very rare. Only a single perfect frustule has been found by me. 
54. Podosira Montag nei Kiitzin7.—Hab. Newport rocks, dredged by Mr. 
Powel. 
