siMPUciA. 4 23 



Others considex' them as organs of respiration *, but that function 

 is most probably exercised by the edges of the umbella. The ten- 

 tacula, Avhether situated on the margin of the umbella or round the 

 mouth, vary, not only according to the species, but the age of the 

 animal f- 



We will unite, under the name of 



Cyan^a, Cuv.f 

 All tlie Medusae with a central mouth and four lateral ovaries. 



C. aurita ; Medusa aurita, L. ; Miill, Zool. Dan. LXXVI,and 

 LXVII. One of the most commonly disseminated species, ac- 

 quiring with age four long arms ; the whole circumference of 

 its imibella is finely ciliated ; reddish branching vessels proceed 

 from the stomach to its circumference. In the 



C. chrysaora ; Med. chrysaora, Cuv., the edges are furnished 

 Avith long tentacula or fulvous or brown lines or spots arranged 

 in radii on its convexity. This species also is extremely com- 

 mon, and varies greatly as to the spots X- 

 We have given the general name of Rhizostojia to that portion of 

 the great genus Medusa which comprises species that liave no mouth 

 opening in the centre, and that appear to live by the suction exercised 

 by their pedicles or tentacula. They have four or more ovaries. 



Rhizostojia, proper. 

 Includes those which are furnished with a central pedicle more or 

 less ramified according to the species. 



The vessels arising from the small ramifications of the pedicles 

 unite in a cavity of its base, whence branches proceed to all parts of 

 the umbella. 



The most common species is the Rhizostome bleu, Cuv., Journ. 

 de Phys., XLIX, p. 436 ; Reaum., Ac. des Sc, I71O, pi. XI, f. 

 27, 28. It is found along the French coast at low water, and its 

 umbella is sometimes almost two feet in width. Its pedicle is 

 divided into four pairs of arms almost infinitely forked and 

 dentated, each one being furnished at base with two auricles 

 that are also dentated; a fine network of vessels extends round 

 the umbella in the thickness of its margin §. 



According to the observations of Messrs. Audouin and Milne 

 Edwards, these Medusse live in society, or at least are always 



* Eisenh., on the Rhisostoma, &.C. 



t See Mull., Zool. Dan., II, p. 01. 



I Most of the Chrysaora of Peroa are mere varieties of this species. — Add Aiirelia 

 crenafa, Chamiss., and Eisenh,. Ac. Nut. Cur., Y., p. I, pi. xxix. 



Besides the Chrysaora, we reJer to this genus the Atjrelia, Cyanea, Obelia 

 and Oceania of Peron : we also include in it Medusa heniisphenca, Mlill., VII. 5 ; 

 Encyc, 93, 8, 11 ; — M. cymhaJoides, Slaber., Encyc., lb., 2 — 4, if we may trust to 

 the characters of such small individuals ; — CaUirhoe hasteriana, Per. ; Baster, Op. 

 Subs., II, V, 2, 3 ; Encyc., XCIY, 4, 5 ; — the Ctjanee bleu, Per. ; Diquemare, Journ. 

 dePhys., 1/84, Dec. 1 ; — the species or varieties fia:ured, but rudely, by Borlassc, 

 Nat. His. of Cornw., pi. xxv, f. 7 — 12, which are referable to our Chrysaora, snd to 

 which should be approximated the Med. ht/sucella,, Gm. ; — M. iyrrhena, Gm., &c. 



§ It is the Pulmo marinus, Mathiol., Aldrov., Zooph., lib. IV, p. 575, the Medusa 



