EXPLANATION OF PLATES. 
PLATE XLI. 
Young and Heron’s map of part of Orange county {Silliman’s Journal, Vol. 21, pp. 
320, 321). 
PLATE XLIL 
INFUSORIA. 
The figures of this plate were drawn by means of the camera lucida, and to the same scale 
as was used in Plates 21 and 22. 
Fig. 1. Synedra-. One group of frustules, with part of another, parasitic on aquatic 
plants in the Hudson River, a, fleshy base ; h, fleshy projection at the summit. 
Brackish water. 
2. Synedra-. a, h, different positions. Fresh water, also fossil. 
3. Podosphenia ? possibly a Gomphonema. Fresh water. 
4. Gomphonema minutissimum. a, largest size; h, smaller individuals. Hudson river 
near West-Point. 
5. Gomphonema-, a. b, different positions ; 6 c, sketch of a group of individuals 
with the branching pedicels. 
6. Gomphonema acuminatum, a, b, different positions. Fresh water, also fossil. 
7. Gomphonema-. 7 a, another view of a frustule. Marine, Stonington, Conn. 
8. Echinella flabellata, a single group. Fig. 8, b, a sketch of several groups slightly 
magnified, drawn from the living specimen. Marine, Stonington, Conn. 
9. Echinella-, a group parasitic on an aquatic plant. Fig. 9, a, b, different posi¬ 
tions of a single frustule. Hudson river. 
10. Cocconema-, group supported on the branching pedicel. Hudson river. 
11. Cocconema-. a, b, two positions of an individual separated from its pedicel. 
12. Achnanthes brevipes, several groups parasitic on a Conferva ; b, a larger pair; c, 
back view. Stonington, Conn., Hudson river, &c. 
13. Striatella arcuata. Marine, Stonington, Conn. 
14. Naunema-. a, b, two positions of the frustule separated from its tube. Marine, 
Staten Island, N. Y. 
15. Naunema-. a, frustule separate from its tube. Stonington, Conn. 
16. Naunema-. a, b, two positions of a single frustule. Stonington, Conn. 
17. Naunema-, group of frustules within their tube. West Point, N. Y. 
17, a. Naunema-, single frustule. West Point. 
18, a to d. Spiculae of Spongilla or fresh-water sponge. 
19, a, b. Probably spiculae of another species of Spongilla; b, group of three indivi¬ 
duals. 
