44 CTENOPHORES OF THE ATLANTIC COAST OF NORTH AMERICA 



radial canals arise directly from the funnel. The 4 meridional subventral 

 vessels are very long and extend around the aboral side of the narrow- 

 edge of the body. The 4 meridional subtentacular canals each give 

 rise to a short tract of cilia and then bend downward and outward along 

 the middle of the sides of the animal and join Avith the meridional sub- 

 ventral canals and the oral forks of the paragastric canals at the extremi- 

 ties of the long sides of the animal. Each of the 2 median tentacles arises 

 from a deep sheath. The sexual products are developed only in the long 

 subventral canals. The larva passes through a Mertensia-like condition 

 in which the tentacular axis is longer than the stomodaeal axis. 

 fri*; Species of Cestum are found in all the warmer oceans. The type 

 species is Cestum veneris Lesueur, of the Mediterranean and tropical 

 Atlantic. "Cesium amphitritis" of Mertens, 1833, appears to be the 

 same species from the tropical Pacific. 



Cestum veneris Lesueur. (Figs. 60 and 61, plate 12.) 



Cestum veneris, Lesueur, 1813, Nouv. Bulletin des Sciences de la Soci6t. Phil., 

 tome 3, p. 281, planche 5, fig. i. — Lesson, 1836, Annates des Sci. Nat., s6r. 2, 

 tome 5, p. 245. — FoL, 1869, Beitrag Anat. Entwick. Rippenquallen, Berlin, 

 p. 8, Tafln. 2-4. 



Cestus veneris, Chun, 1880, Ctenophoren des Golfes von Neapel, pp. 53, 135, 152, 

 181, 301, Taf. 11-13 (full list of literature). — Allman, 1881, Journal Linnean 

 Soc, London, vol. 16, p. 106. — Chun, 1898, Ctenophoren des Plankton-Exped., 

 p. 20. — Graeffe, 1884, Arbeit. Zool. Inst. Wien, Bd. 5, p. 362. — Wagner, 

 N., 1885, Die Wirbellosen des Weissen Meeres, p. 54. — Romer, 1903, Fauna 

 Arctica, Ctenophoren, Bd. 3, p. 85. — Vanhoffen 1906, Nordisches-Plankton, 

 Ctenophoren, 11, p. 6, Fign. 14, 15. — Samassa, 1892, Archiv fiir mikroskop. 

 Anatomie, Bd. 40, pp. 169, 218 (histology). — Moser, 1908, Abhandl. Akad. 

 Mtinchen, Suppl. Bd. i, Abhandl. 4, p. 12. 



Cestum amphitrites, Mertens, 1833, M^m. Acad. Sci. St. P^tersbourg, Sci. Math. 

 Phys. et Nat., s€v. 6, tome 2, p. 492, Taf. i (tropical Pacific). 



Cestus pectenalis, Bigelow, 1904, Bull. Museum Comp. Zool. at Harvard College, 

 vol. 39, p. 267, plate 8, fig. 30 (Indian Ocean). 



The animal is fiat and ribbon-shaped, being about So mm. high and 

 sometimes over 1,500 mm. wide, although specimens over 800 mm. in 

 width are not common. The body is strongly compressed in the ten- 

 tacular diameter. The apical sense-organ is a simple capsule containing 

 a cluster of concretions, and is slightly depressed beneath the general 

 level of the body surface. The long, narrow aboral side of the animal 

 is arched and bears small, wart-like protuberances. The ventral, ten- 

 tacle-bearing edge is much narrower than the aboral edge, and the sides 

 bulge slightly outward so that the animal is widest midway between 

 mouth and apex. The subtentacular rows of combs are represented by 

 4 short tracts close to the sides of the sense-organ. Beyond these there 

 is a short, free interval, and then commence the 4 long subventral rows 

 of combs which extend along the sides of the arched aboral edge of the 

 animal. Simple tentacles, closely set in a double row, extend along 

 the sides of the oral edge of the animal, following the courses of the oral 

 branches of the paragastric canals. 



The stomodaeum is cruciform in cross-section, being slightly out- 

 folded in the tentacular (funnel) axis, although wider in the sagittal 

 axis. The funnel is about one-third to one-fourth as long as the height 

 of the animal, becoming relatively shorter as the animal increases in 

 .size. The 4 slender, interradial canals arise from the funnel, as do also, 



