CTENOPHORES OF THE ATLANTIC COAST OF NORTH AMERICA 19 
Genus LESUEURIA Milne-Edwards, 1841. 
Lesueuria, MitNE-Epwarps, H., 1841, Annal. des Sci. Nat., sér. 2, tome 66, p. 
199.—LEsson, 1843, Hist. Zooph. Acal., p. 90.—Acassiz, L., 1860, Cont. Nat. 
Hist. U. S., vol. 3, p. 290.—Acassiz, A., 1865, North Amer. Acal., p. 23.— 
Cuun, 1880, Ctenophoren des Golfes von Neapel, pp. 290, 291.—VANHOFFEN, 
1906, Nordisches Plankton, Ctenophoren, p. 4.—Moser, 1908, Abhandl. 
Akad, Munchen, Suppl. Bd. 1, Abhandl. 4. 
GENERIC CHARACTERS. 
Lobate with rudimentary oral lappets and with long, ribbon-shaped 
auricles. The peripheral gastro-vascular system is simple, without 
complex windings. 
The type species is Lesueuria vitrea of the Mediterranean. 
The so called American species L. hyboptera is said to be more nearly 
rectangular in outline than the oval-shaped L. uitrea of Europe. In the 
American form the body is wider both above and below than it is in the 
‘middle, thus giving it somewhat the appearance of a laterally flattened 
hour-glass. 
Lesueuria hyboptera A. Agassiz. 
Lesueuria hyboptera, Acassiz, A., 1865, North Amer. Acalephe, p. 23, figs. 25-28.— 
VANHOFFEN, 1895, Bibliotheca Zoologica, Heft 20, Lfg. 1, p. 18. 
The body of the adult animal is 100 mm. long, while the broad side 
(stomodzal axis) is 50 mm. and the narrow side (funnel-axis) is 30 mm. 
‘The lateral compression is thus almost as great as in Mertensia, but of 
reverse character, the gastric axis of Mertensia being the narrower. 
The body is widest at about the level of the mouth. The apical sense- 
-organ lies at the bottom of a narrow cleft about 12 mm. in depth. The 
4 subtentacular rows of ciliated combs are each about half as long as the 
‘body and terminate near the bases of the 4 auricles. These auricles are 
very large, being almost 50 mm. in length. They are wide and ribbon- 
. shaped and their free edges are lined with a row of hair-like cilia. The 
_4 subventral rows of ciliated combs are longer than the 4 subtentacular 
‘rows and extend over fully three-fourths of the length of the body. The 
2 oral lappets are short and blunt, being not more than one-tenth as 
long as the body of the animal. This bluntness imparts an almost rec- 
‘tangular appearance to the creature when seen from the broad side. 
The stomodeum is long and narrow, while the funnel-tube is very short. 
~The tubes of the peripheral canal-system are extremely narrow and 
-exhibit no complex windings. The 4 subtentacular meridional vessels 
wind somewhat as they enter the auricles, while the 4 subventral merid- 
‘ional tubes are quite straight and do not wind as they extend through 
the substance of the oral lappets. The animal is almost transparent, 
‘being of a slightly milky hue. It gives rise to an intense steel-blue 
-phosphorescence when disturbed at night. 
This species must be a very rare and occasional visitor to our 
-coast. A. Agassiz found it in great numbers in Massachusetts Bay and 
Newport Harbor about 1860, but it has never been seen since that time. 
It is interesting to notice that M’Intosh, 1888 (Ann. and Mag. Nat. Hist., 
ser. 6, vol. 2), reports the sudden appearance of great swarms of a species 
of Lesueuria, possibly Bolinopsis ?, off the coast of Scotland. The fore- 
_going description is derived entirely from A. Agassiz, who is the only 
