CTENOPHORES OF THE ATLANTIC COAST OF NORTH AMERICA 35 



for Rang, 1828, applied it to designate a Mnemiopsis-like ctenophore. 

 Leucothea Mertens, 1833, is thus the oldest distinctive name applied to 

 the genus. 



The genus Leucothea is distinguished from all other Ctenophorae 

 by the 2 remarkable blindly-ending sacs which form a pair of long narrow 

 pits open to the outer world below and extending inward and upward 

 from above the tentacle-bulbs nearly to the level of the funnel. 



The type species is Leucothea multicornis of the Mediterranean. 

 This species is most admirably figured and described by Chun, 1880 

 (Ctenophoren des Golfes von Neapel, pp. 47, 122, 143, 151, 242, 296, 

 Taf. 4, 5 and 9), who found that when the water was unusually warm the 

 larvffi just out of the egg and still in the Cydippe-stage produced ripe 

 ova which developed into normal but small embryos, resembling those 

 produced by the adult except that they were only about half the normal 

 size. 



Leucothea ochracea sp. nov. (Figs. 49 to 54, plates 9, 10.) 



Euckaris multicornis, Fewkes, 1882, Bull. Museum Comp. Zool. at Harvard Col- 

 lege, vol. 9, p. 251, plate 7, figs. II, 12. 



This Florida species differs from the Mediterranean Leucothea multi- 

 cornis in its smaller size and simpler windings of the meridional ventral 

 canals through the oral lobes, and by having 4 prominent, yellow areas, 

 a pair in the gelatinous substance of the outer sides of each lobe ; but it 

 is chiefly distinguished by having simple, lateral filaments upon its prin- 

 cipal tentacles, these being absent in the Mediterranean species. 



It will be remembered that Chun, 1880, found that the larva of the 

 Mediterranean Leucothea passes through a Cydippe-like stage wherein it 

 has a pair of tentacles provided with lateral filaments as in Mertensia or 

 Pleurobrachia. Later the larva passes into a medusiform stage, in which 

 it completely loses its tentacles, and next it passes into a Bolinopsis stage 

 in which the tentacles reappear, but without lateral filaments. The 

 Leucothea stage then ensues, wherein the papillae develop over the sur- 

 face of the body and the blind sacs sink inward into the sides of the body 

 above the bases of the 2 principal tentacles. 



I have seen Leucothea multicornis in considerable numbers at Naples, 

 and have never observed lateral filaments upon the tentacles of the adult, 

 nor does Chun mention or figure them in his superb monograph. Their 

 constant presence in the Tortugas ctenophore may therefore be con- 

 sidered as of specific significance. Also I have never seen \'elIow areas 

 on the sides of the oral lobes in the Mediterranean Leucothea nor does 

 anyone figure them, but these are very characteristic of the Florida 

 Leucothea ochracea and render it a conspicuous object as it floats in the 

 water. 



The dimensions of the Florida L. ochracea as compared with those 

 of the Mediterranean L. multicornis are here given in millimeters. The 

 dimensions of the Mediterranean ctenophore are taken from a specimen 

 studied by me at Naples on December 8, 1907. According to Chun, 

 however, the Mediterranean Leucothea becomes about 200 mm. long and 

 240 mm. across the oral lobes, thus becoming much larger than the 



