196 MEDUS.E OF THE WORLD. 



sented to me by the Department of Biology of fohns Hopkins University for publication in 

 this work, and it seems but fitting that the species should be named in honor ot the great 

 naturalist who discovered it. It is closely allied and possibly identical with the European 

 ffillsia stellata, although the 3-rayed center of the stomach appears to distinguish it. 



In the young stage there are 6 simple, slender radial-canals, 60 apart. The beU-walls 

 are relatively thin and the bell somewhat higher than a hemisphere with a bluntly pointed 

 apex. The 6 tentacles are 5 to 6 times as long as the bell-diameter and have swollen, 

 nematocyst-bearing, outer extremities. 



In the mature medusa the bell is flatter than a hemisphere, thick walled, with a shal- 

 low bell-cavity. Twenty-four tentacles alternate with 24 exumbrella, nematocyst tracts 

 each with several clusters of nettling cells. The manubrium has 6 lips. Stomach j-rayed 

 at center, but each ray forks, giving 6 ramuli, 6 primary radial-canals which bifurcate twice 

 giving 24 terminal branches. The gonads extend along the sides of the stomach. The 

 size and color can not be determined from Professor Brooks's drawings. Found at Beau- 

 fort, North Carolina. (See page 195.) 



Order LEPTOMEDUSJE Haeckel, 1866. 



Lefilomtduij-, HAECKEL, 1866, Gencrellen Morphologic, BJ. 2, p. Ivii; 1879, Syst. dor Meduscn, p. 1 1 1 . BIGILOW, njo'j, 

 Mem. Mus. Comp. Zool. at Harvard College, vol. 37, p. 147. TORREY, 1909, Publications University California, Zool., 

 vol. 6, p. 12. 



CHARACTERS OF THE ORDER l.EPTOMEDUS^E. 



Hydromedusae which arise by alternation of" generations from Campanularian hydroids. 

 The gonads are developed upon the radial-canals. When present the lithocysts are of ecto- 

 dermal origin. 



We may distinguish three families as follows: 



1. Thaumantiadae Gegenbaur, 1856. Without lithocysts, but with marginal sensory- 



clubs or cordyli. 



2. Eucopidx Gegenbaur, 1856. With lithocysts and with less than 8 radial-canals. 



3. yEquoridae Eschscholtz, 1829. With lithocysts and with more than 8 radial-canals. 



The Leptomedusae are probably descended from the more simply organized Antho- 

 medusae; this is shown by the fact that when first set free from the hydroid some of the Euco- 

 pidae, such as Phortis,lzck lithocysts, which develop later. Also the hydroid of Eutinn called 

 Campanopsis has nearly all of the characters of the Tubularian hydroids. Asexual production 

 of medusa-buds is extremely rare in the medusa? of the order Leptomedusae being known only 

 in Eucheilota paradox tea and Eirenc incJusifera. These medusae are therefore creatures of 

 the coasts and are rarely found far out at sea, for they can not maintain themselves in 

 situations unsuited to the growth ot their hydroids. 



Family THAUMANTIADjE Gegenbaur, 1856. 



Thaumantiada, GEGENBAUR, 1856, Zeit. fiir wissen. Zoo]., Bd. 8, pp. 218, 236, 268. MAAS, 189}, Ergeb.der Plankton Exped., 

 Bd. 2, K. c., pp. 64-65; 1897, Mem. Mus. Comp. Zool. at Harvard College., vol. 23, No. i, p. 19; 1905, Craspe- 

 doten Medusen der Siboga Expedition, Monog. 10, p. 23. 



ThaumanliaJit+Cannolicif, HAECKEL, 1879, Syst. der Medusen, pp. 120, 140. 



FAMILY CHARACTERS. 



Leptomedusae without lithocysts. The gonads are developed upon or extend outward 

 over the radial-canals and are not confined exclusively within the walls of the stomach. 



In so far as is at present known the Thaumantiadae develop through alternation of 

 generations from Campanularian hydroids. For our knowledge of the development of the 

 species constituting this family we are indebted to the researches of Wright, 1862, on Thau- 

 mantias; A. Agassiz, 1865, on Melicertum; Metschnikoff, 1886, on Laodicea; and Browne, 

 1900, on Dipleurosoma. 



It is evident, indeed, that the Thaumantiadae are very closely related to the Eucopidae. 

 They resemble the Tubularian medusae (Anthomedusae), however, in the absence of lithocysts 

 and the prevalence of ectodermal ocelli upon the tentacle-bulbs. Indeed, all authorities agree 

 in considering the Thaumantiadae as more lowly organized than the Eucopidae and /Equorid;p. 



