444 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



the surface of the water. ''During the day they often remain sus- 

 pended for hours in the water simply by spreading their wing-like ap- 

 pendages, and then suddenly drop to the bottom on folding them." Mr. 

 Agassiz captured the specimens upon which his observations were made, 

 at Nahant, Massachusetts, during the summer of 1869, and judging 

 from the figures in Binney's Gould they were probably specimens, not 

 quite adult, of this species. He has also taken adult specimens at 

 Newport. Mr. S. I. Smith captured full grown specimens in the edge 

 of the Gulf Stream, off St. George's Bank, and we have specimens taken 

 from the stomach of mackerel, caught twenty miles south of No Man's 

 Land. 



The CavoUna tidentata (Plate XXV, fig. 177) is a beautiful and curious 

 species, with a singularly shaped, amber-colored, translucent shell, much 

 larger than that of either of the preceding species. We did not observe 

 it living in these waters, but the shells were twice dredged off Martha's 

 Vineyard, and one of them was perfectly fresh and glossy, as if just 

 dead. It is a southern species which comes north in the Gulf Stream, 

 but it had not been found previously on the coast of New England. 

 Another Gulf Stream species, the Diacria trispinosa, is occasionally 

 found at Nantucket, according to Dr. Stimpson, but whether it has been 

 observed there alive is uncertain j eight or nine other species were taken 

 in the Gulf Stream, off St. George's Bank, by Messrs. Smith and Har- 

 ger in 1872, all of which may, perhaps, occasionally occur about Martha's 

 Vineyard and Nantucket. 



Another very interesting and beautiful Pteropod, the CUoiie papilio- 

 naceaj was taken in considerable numbers at Watch Hill, Ehode Island, 

 April 13, by Professor D. 0. Eaton and myself. They were swim- 

 ming at midday near the surface, associated with PleiirohracMa rhodo- 

 dactyla, and appeared to be common at that time. Mr. Vinal N. 

 Edwards obtained two specimens in Vineyard Sound, April 30. 

 This difiers from those named above, in being destitute of a shell, as 

 well as in many other characters. The body is stout, somewhat fusi- 

 form, tapering gradually to the pointed posterior end ; in the largest 

 specimens the length was about 1.5 inches. The head is rounded, with 

 two small conical processes in front, on the upper side. Six tentacle- 

 like organs, or " arms," bearing minute suckers, can be protruded. The 

 wings or fins are large and broad oval in outline. 



The bod}^ and wdngs are pale, transparent bluish, with opalescent 

 hues 5 the mouth and parts around it, the " arms," and part of the 

 head, and some of the internal organs, are tinged with orange; the 

 posterior part of the body is bright reddish orange, for nearly half an 

 inch. Some of the internal organs are orange-brown and olive-brown, 

 and show through the transparent integuments as dark patches. This 

 species has seldom been observed on our coast. Dekay, in 1843, men- 

 tioned its occurrence in a single instance, off New York. In 18G0, it 

 was taken in considerable numbers at Portland, Maine, by Mr. C. B. 



