I see at the Aquarium

May 3. 

To Cambridge and Boston. 

I see at the Aquarium many of my little striped or barred breams, now labelled Bryttus esobus. Compared with the common, they have rounded tails, a larger dorsal and anal fins, and are fuller or heavier forward. I observe that they incline to stand on their heads more. 

The proprietor said that some little fishes one and a half to two inches long, with a very distinct black line along the sides, which I should have called brook minnows, Agassiz was confident were young suckers, but Mr. Putnam thought that they were the Leuciscus atronarus, i. e. my brook minnow. 

I observe that a leuciscus  probably pulchellus, if not argenteus), five inches long, also has a broad line along the side, but not nearly so dark. 

He shows me the eudora (water-plant), which he has not seen east of the Connecticut.

H. D. Thoreau, Journal, May 3, 1860

At the Aquarium. See  May 1, 1858 ("I see many minnows from three quarters to two inches long, but mostly about one inch. They have that distinct black line along each side from eye to tail on a somewhat transparent brownish body, dace-like, and a very sharply forked tail. . . . Is it not the brook minnow?"); April 27, 1859 ("Saw at the Aquarium in Bromfield Street apparently brook minnows with the longitudinal dark lines bordered with light"). See also March 29, 1854 ("poised over the sand on invisible fins, the outlines of a shiner. . . distinct longitudinal light-colored line midway along their sides and a darker line below it”); July 17, 1856 (“They have . . . a broad, distinct black band along sides (which methinks marks the shiner)"); December 11, 1858 (“a minnow — apparently a young shiner, but it has a dark longitudinal line along side ”); December 18, 1858 (“They are little shiners with the dark longitudinal stripe”)