514 



REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



[2] 



As more and more is known of the niednsan 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^e. 



Family RHIZOPHYSID^. 



Pterophysa, 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 it 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 Ehizophysid in this and certain other 

 features of the anatomy, which are well marked in the new specimeus 

 recently collected. In the collection of 1883 a giant float was found, 

 which, although at that time not recognized as belonging to Ptero- 

 physa, 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 ( u Rhizo- 

 physa") mentioued 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 Ehizophysid. The specimens are as follows: 



Of the new specimens, No. 1 is the best preserved and the largest. 

 Both were found twisted on the dredge wire or rope. Neither of the 



* Letter No. 3. Bull. Miis. Conip. Zool. Vol. V, No. 14, pp. 289-290. 



