SEMAEOSTOME/E— AURELLIA. 619 



Genus AURELLIA P€ron and Lesueur, 1809. 



(?) Evai^ora, P^ron t:T Llsueur, 1809, Ann. tlu Mus. Hist. Nat., Paris, tome 14, p. 343. 



Aurelliti, Ibid., p. 357. 



Ocyroc, Ibid., p. 355. 



Orythia, Lamarck, 1816, Hist. Anini. sans. Vert., tome 2, p. 502. Aurclia, Ibid. p. 512. 



Medina, EscHScHOLTZ, 1829, Syst. der .Acalcphen, p. 61. 



Monocnupedon+Diflocraipedon, Brandt, 1S38, Mem. .•Xcaii. Imperiale des Sci. St. Petcrsbourg, Sci. Nat., ser. 6, tome 4, pp. 



370, 371- 



Biblis, Lesson, 1843, Hist. Nat. des Zoophytes, p. 339. 



Claustni, Ibid., p. 378. 



Aurelia, .'Vgassiz, L., 1862, Cont. Nat. Hist. U. S., vol. 4, pp. 11, 72, 78, 159. — Acassiz, A., 1865, North .Amcr. .Acal., p. 41. — 

 CiAus, 1877, Dcnlis. Akad. Math. Naturwiss., Wien., Bd. 38, p. 19. — Haf.ckel, 1880, Syst. der Medusen, pp. 551, 644; 

 1881, Metagenesis und Hvpogenesis von Aurelia aurita, Jena, 36 pp., 2 taf. 



Aurelia, vo.n Lf.ndenfeld, 1884, Proc. Linnean Soc. New South Wales, vol. 9, p. 279. — Goktte, A., 1887, Abhandl. zur Ent- 

 wickelungsgesch. Thiere, Heft 4, Leipzig (embryology). — .\gassiz and Mayer, 1899, Bull. Mus. Comp. Zool. at Harvard 

 College, vol. 32, p. 171. — Vanhoffen, 18SS, Bibliotheca Zoologica, Bd. 1, Heft 3, p. 23. — Bateson, 1895, Materials for 

 the Study of Variation, p. 428 (variations). — Browne, 1894, Quart. Journ. Micros. Sci., vol. 37, p. 245. — Hvdf, 1894, 

 Zeit. fiir wissen. Zool., Bd. 58, p. <;3t;. — Vanhoffen, 18S8, Bibliotheca Zoologica, Heft 3, p. 19; 1902, Wisscn. Ergeb. 

 deutsch. Tiefsee Expedition, Dampfer J'aldivia, Bd. 3, Lfg. 1, p. 41; 1906, Nordischcs Plankton, Nr. 11, p. 60. — Maas, 

 1906, Fauna .Arctica, Bd. 4, Lfg. 3, p. 507 (discussion of literature); 1903, Scyphomedusen tier Siho^^a Expedition, Monog 

 II, p. 26. — Friedm.ann, 1902, Zeit. fiir wissen. Zool., Bd. 71, p. 227. — Hargitt, 1905, [ourn. Exper. Zool., vol. 2, p. 548. 



Auricoma, Haeckel, 1880, loc.cil., pp. 633, 644 (an abnormal Aurellia with 16 sense-organs). 



GENERIC CHARACTERS. 



Ulmaiidas with a simple, central mouth-openini!; which is surrounded by 4 well-developed, 

 radially situated, unbranched mouth-arms or palps. 8 marginal sense-organs. The tentacles 

 are small and alternate with an equal number of short lappets. Both tentacles and lappets 

 arise from the sides of the exumbrella a short distance above bell-margin. The bell-margin 

 is divided into 8 or 16 broad, velar lobes. The central stomach siives rise to a number ot 

 branched, radiating canals which anastomose and are connected by a marginal ring-canal. 

 There are 4 interradial gonads and 4 well-developed, subgenital pits. 



The name " Evagora" which takes precedence over "/Itirellui" was applied to ForskSrs 

 medusa persea which is whollv unrecognizable, as is also ''Ocyfoe," and these names must 

 therefore yield to "Aurellia," which was first proposed by Peron and Lesueur tor .lurellia 

 aurtta of Europe. They spell the generic name Aurellia. 



The species of this genus are among the most widely distributed ot Scvphomedusae, being 

 found in all oceans and all latitudes. They are most abundant along the shores ot continents 

 and large islands and are comparatively rare in the open ocean far from land. It is possible 

 that the fossil Medustna costata from the lower Cambrian of Sweden is an Aurellia. 



.Although fully a dozen species oi Aurellia have been described I believe that there are but 

 3 reasonably well-defined types. Of these A. aurita is of world-wide distribution. A. labiata 

 is found in the Pacific, and a third fairlv well-defined species is ."/. maldivensts, described by 

 H. B. Bigelow from the atolls of the Maldive Islands in the Indian Ocean. The distinctions 

 between man)- of the "species" are not well ascertained, and there are numerous varieties or 

 local races. A. aurita is subject to great individual variation and some of these chance varia- 

 tions have been described as species. 



The species oi Aurellia displav much individual variabilitv, and studies upon this subject 

 have been carried out by Ehrenberg ( 1835), Romanes (1876-77), Browne ( 1894-95), Duncker, 

 Sorby, Herdman, Unthank (1894), Ballowitz (1898), and Hargitt (1905). Good reviews of the 

 results of the earlier of these investigations are given bv Bateson, 1895 (Materials for the Study 

 of Variations, p. 426), and by Agassiz and Woodworth, 1896 (Bull. Mus. Comp. Zool. at 

 Harvard College, vol. 30, No. 2). The abnormal individuals of /-/i/jv/Z/rt aurita are peculiar in 

 that they generally preserve the radial symmetry of the disk, even though the number of 

 segments be changed. Radially svmmetrical abnormalities appear to be about twice as 

 numerous as are irregular ones. This law applies also to the variations of the Leptomedusa 

 Pseudoelytia petitata (see vol. II, p. 278). 



Browne, 1894 and 1895, discovered that congenitally abnormal ephyrae oi Aurellia survived 

 fully as well as normal ones, and also that the abnormal ephyrae were no more abundant in 

 1892 than they were when Ehrenberg studied them at the same place in 1834. Evidently the 

 abnormal individuals do not actjuire anv fixed tendency to perpetuate their own peculiarities 



