CTENOPHORES OF THE ATLANTIC COAST OF NORTH AMERICA 43 



Order CESTID^ Gegenbaur, 1856. 



Callianirida, Eschscholtz, 1829, Syst. der Acal., p. 21. 

 CestoidecB, Lesson, 1843, Hist. Zooph. Acal., p. 68. 

 CestidcE, Gegenbaur, 1856, Archiv fur Naturgesch., Jahrg. 22, p. 196. 

 TaeniatcE, Agassiz, L., i860; Cont. Nat. Hist. U. S., vol. 3, p. 292. 

 CestidcB, FoL, 1869, Beitrag Entwick. einigen Rippenquallen, p. 6. 

 CesttdcB, Chun, 1880, Ctenophoren des Golfes von Neapel, p. 300. — Vanhoffen, 

 1906, Nordisches Plankton, Ctenophoren, xi, p. 6. 



CHARACTERS OF THE ORDER. 



Ribbon-shaped ctenophoras in which the tentacular axis is mark 

 edly compressed and the lobular axis correspondingly extended. The 4 

 subtentacular rows of combs are rudimentary and the 4 subventral rows 

 greatly extended. The axial tentacles have basal-sheaths. 



Thus in the Cestidae we find an extraordinary development of the 

 lateral compression seen in lesser degree in the Lobatse. The funnel- 

 axis is thus reduced and the stomodaeal axis greatly extended. This 

 causes the subtentacular rows of combs to be rudimentary while the sub- 

 ventral rows are correspondingly lengthened. The sheaths of the median 

 tentacles recall the conditions seen in the Cydippidas, and indeed the 

 larvae of the Cestidae when hatched from the eggs are Mertensia-like in 

 appearance with the tentacular axis longer than the sagittal, this being 

 the reverse of the condition which pertains in the adult. 



There are two genera, Cestum and Folia. In Cestum the narrow, 

 aboral edge of the animal is arched and the 4 subtentacular meridional 

 canals extend upward from their points of origin and are provided each 

 with a very short tract of cilia. They then bend downwards and finally 

 outwards along the middle of the sides to the ends of the body, where 

 they join the 4 meridional subventral canals. In the genus Folia the 

 aboral narrow edge is flat and the 4 subtentacular meridional canals 

 do not arch upward, but extend straight outward to the ends of the sides 

 of the body. 



The oral branches of each paragastric canal fuse with the meridional 

 vessels of their own side only, and thus the peripheral canal-system of 

 each broad side of the body is separated from that of the other side; 

 there being no circum-oral canal such as is seen in the Lobatae. 



Species of Cesium are found in all of the warm oceans. Folia is 

 represented by F. parallela of the Mediterranean and tropical Atlantic. 



Genus CESTUM Lesueur, 1813. 



Cestum, Lesueur, 1813, Nouv. Bull, des Sci., tome 3, p. 281. — Eschscholtz, 1829, 

 Syst. der Akalephen, p. 23. — Mertens, 1833, M^m. Acad. Sci. St. P^ters- 

 bourg, s^r. 6, tome 2, p. 492. — Milne-Edwards, 1857, Annal. des Sci. Natur- 

 elles, Zool., s6r. 4, tome 7, p. 291. — Fol, 1869, Anatomie und Entwick. der 

 Rippenquallen, p 8. — Bigelow, 1904, Bull. Museum Comp. Zool. at Harvard 

 College, vol. 39, p. 267. 



Cestus, Chun, 1880, Ctenophoren des Golfes von Neapel, p. 301. — Vanhoffen, 

 1906, Nordisches Plankton, Ctenophoren, xi, p. 6. 



GENERIC CHARACTERS. 



Cestidae in which the great extension of the sides in the stomodaeal 

 axis and the marked compression of the body in the tentacular axis 

 cause the animal to assume the shape of a long, flat ribbon. The 4 inter- 



