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 Avaters, 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 

 Ampulariae. 



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 brine 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. 



