10 CTENOPHORES OF THE ATLANTIC COAST OF NORTH AMERICA 
Pleurobrachia pileus Vanhoffen. 
Beroé pileus, FaBrictus, 1780, Fauna Gronlandica, p. 361, Nr. 354. 
Beroé globigereux, CUVIER, 1817, Régne Animal, tome 4, p. 59. 
ee pileus, GOULD, 1841, Report Invert. Mass., p. 349.—Morcu, O., 1857, 
eskriv. af Grénland, p. 97. 
Pleurobrachia rhododactyla, Acassiz, L., 1849, Mem. American Acad., vol. 4, part 
10, p. 314, plates 1 to 5; ibid., 1860, Cont. Nat. Hist. U.S., vol. 3, pp. 203, 
294; plate 2a.—Stimpson, W., 1853, Marine Invert. Grand Manan, p. 11.— 
Acassiz, A., 1865, North Amer. Acal., p. 30, figs. 38 to 51; Ibid., 1874, Mem. 
American Acad., vol. 10, No. 3, pp. 372 to 374, plate 3, figs. 25, 25’; plate 4, 
figs. 1 to 45; plate 5, figs. 1 to 32.—FEWKES, 1884, Mem. Museum Comp. 
Zool. at Harvard.College, vol. 9, No. 3, plate 9, figs. 8 to 9, 14 to 37. 
Pleurobrachia rhododactyla and P. pileus, VANHOFFEN, E., 1895, Bibliotheca Zoo- 
logica, Heft 20, Lfg. 1, pp. 15, 17, 21.—CURRERI, 1900, Boll. Soc. Ital. Zool., 
Roma, Anno 9g, p. 192. 
Pleurobrachia pileus, Cuun, C., 1898, Ergeb. der Plankton-Expedition, Ctenophoren, 
p. 15.—GRaBE, 1901, Zeit. fiir wissen. Zool., Bd. 69, p. 486, Taf. 36, 37 (develop: 
ment of sexual organs).—R6MER, 1903, Fauna Arctica, Ctenophoren, Bd 3, 
p. 75 (full list of literature) —MosEr, 1903, Ctenophoren der Sinedatenedt 
tion, p. 5 (list of literature); also, 1908, Zool. Anzeiger, Bd. 33, p. 756.— 
PARKER, 1905, Journal Experimental Zool., vol. 2, p. 409 (movements of 
swimming plates, see Mnemiopsis)—BRrownkE, 1905, Bron. Royal Soc. Edin- 
burgh, vol. 25, p. 784.—MosEr, 1909, Ctenophoren der deutsche Stidpolar- 
Exped., Bd. 11, p. 141.—Ghigi, 1909, Ctenofori, Roy. Instituto Studi upe- 
riori, Firenze, vol. 2, fasc 1, p. 9.—Evans and Ashworth, 1909, Proc. Roy. 
Physical Soc., Edinburgh, vol. 17, p. 308. : 
Pleurobrachia bachei, Acassiz, L., 1860, Cont. Nat. Hist. U. S., vol. 3. p. 294.— 
Acassiz, A., 1865, North American Acal., p. 34.—ToRREY, 1904, Univ. 
California Publications, Zool., vol. , p. 46, plate 1, fig. 3. 
The body is egg-shaped, or almost spherical, and about 17 to 20 
mm. in length and 14 to. 18 mm. wide in the tentacular axis. Evans and 
Ashworth, 1909, record a specimen 30 mm. in length from Burntisland 
Harbor, Scotland, in December. It is only slightly compressed later- 
ally in the plane transverse to the tentacular diameter, so that the 
lateral diameters are to each other as about 10 to 12.5, the tentacular 
axis being the wider. The apical sense-capsule is situated upon the 
surface and is not sunken within a niche. It incloses a small, spherical 
mass of concretions and is not surrounded by protuberances, the 
outer surface of the apical pole-plate being smooth. The eight rows 
of ciliated plates are about equal in length each to each and extend 
from points quite near the apical sense-organ, about three-quarters the 
distance down the sides of the body. Each subtentacular row contains 
about 38 combs of cilia, and each subventral row 35. The 2 tentacles 
arise from 2 deep clefts in the sides of the body which serve as sheaths 
into which the entire contractile portion of the tentacles may be with- 
drawn. The tentacle-bulbs are widely separated from the sides of the 
paragastric canals. When they are fully expanded the tentacles may be 
15 to 20 times as long as the body and have a linear row of numerous sim- 
ple, lateral filaments which give them a delicate, feathery appearence. 
They are highly contractile and extremely sensitive and are constantly 
changing their appearance as the animal moves through the water, at 
times being drawn up into knotted, string-like masses, and at other 
times being stretched far out in graceful, sweeping curves with their 
lateral filaments giving them the appearance of the most exquisite one- 
sided feathers. The mouth is a long, narrow slit, its wide axis being 
perpendicular to the plane passing through the tentacles. The stomo- 
