240 A JOURNEY IN BRAZIL. 
dawn, on a fishing excursion with Major Estolano, and 
returned with numerous specimens of a new species of 
America; such as Hyria, Castalia, and Mycetopus, to which I would add 
another genus, founded upon slender, sickle-shaped Unios, common to North 
and South America. But what seems to have escaped the attention of con- 
chologists is the striking resemblance of Hyria and Avicula, of Castalia and 
Area, of Mycetopus and Solen, &c. Thus exhibiting another repetition of 
marine types in a family exclusively limited to fresh waters, and having struc- 
tural characters of its own, entirely distinct from the marine genera,, the 
appearance of which they so closely ape. In this connection I cannot suppress 
the remark, that it would be puerile to consider such mimicry as indicative of 
a community of origin. Some of the land shells even recall marine forms ; 
such are some of the Bulimus tribe, which resemble the genus Phasianella and 
Littorina far more than their own relatives. The similarity of the fringes of 
the anterior margin of the foot is particularly striking. The Ampullarire 
remind one also, in a measure, of the marine genera Struthiolaria, Natica, 
&c., and many fossils of the latter family have been confounded with fresh-water 
Ampularise. 
The most noticeable feature of the Amazonian fauna, considered with refer- 
ence to its oceanic character, is, however, the abundance of Cetaceans through 
its whole extent. Wherever I have navigated these waters, from Para, where 
the tides still send the salt bi'ine up the river, to Tabatinga on the borders 
of Peru, in all the larger and smaller tributaries of the great stream as well 
as in the many lakes connected with their ever-changing course, I have seen 
and heard them, gamboling at the surface and snoring rhythmically, when 
undisturbed in their breathing. At night, especially, when quietly at anchor 
in the river, you hardly ever fail to be startled by the noise they make, when 
reaching the surface to exhale forcibly the air they have long retained in their 
lungs while under water. I have noticed five different species of this order 
of animals in the waters of the Amazons, four of which belong to the family 
of Porpoises and one to that of Manatees. Mr. Burkhardt has drawn three 
of them from fresh specimens for me, and I hope before long to secure equally 
.faithful representations of the others, when I shall describe them all com- 
paratively. One of the Porpoises belongs to the genus Inia, and may be 
traced on the upper tributaries of the Amazons to Bolivia, another resem- 
bles more our common Porpoise, while still another recalls the Dolphin of 
the sea-coast ; but I have been unable to ascertain whether any one of them 
is identical with the marine species. At all events, the black Porpoise of the 
bay of Marajo, frequently seen in the vicinity of Para, is totally different from 
the gray species seen higher up the stream. L. A. 
