514 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [2] 
As more and more is known of the medusan life of the Gulf Stream, 
we see how rich in new genera the waters of this current are, and what 
a good collecting locality it presents for a discovery of new genera, 
species, and even families of these pelagic organisms. 
This paper, like those with a similar title which have preceded it, is 
preliminary to a final report on North American Hydrozoa, which the 
author has in preparation. 
SIPHONOPHORA. 
PNEUMATOPHOR. 
Family RHIZOPHYSID/. 
Preropuysa, Fewkes. 
In the collection of 1883 a Siphonophore was recorded, to which, from 
the peculiar wings or ptera on the polypites, the name Pterophysa was 
given. 
The stem of this specimen is very much twisted, and the float and 
other portions so contracted that if was impossible for me to make out 
the anatomy of any part except polypites. The wings of the polypites 
are, however, so exceptional, that it seemed justifiable to refer this spec- 
imen on this ground to a new genus. 
Pterophysa differs from any Rhizophysid in this and certain other 
features of the anatomy, which are well marked in the new specimens 
recently collected. In the collection of 1883 a giant float was found, 
which, although at that time not recognized as belonging to Ptero- 
pliysa, after study of new material is thought to belong to this genus. 
Among the collections made by Mr. A. Agassiz, in the Blake, there is 
also a huge Siphonophore, which has ptera on the polypites, and seems 
to belong to the same genus. These are the physophores (‘Rhizo- 
physa”’) mentioned by A. Agassiz in a letter to the Superintendent of 
the Coast Survey.* 
In the collections of the Albatross, in 1885, there are fresh specimens 
of Pterophysa, which throw light on some points in the anatomy of 
this curious Rhizophysid. The specimens are as follows: 


Catalogue | 
number. Station. | 
reat ea eee ae 
ee meee ts et 10435 | 2398 | 
ce 
eee 11685 | 2570 =| 
| 
Of the new specimens, rine! ag tna tiost dn preserved and the largest. 
Both were found twisted on the dredge wire or rope. Neither of the 
* Letter No.3. Bull, Mus. Comp. Zoil. Vol. Yv, No. 14, pp. 289-290, 


