46 Bulletin, Vanderbilt Marine Museum, Vol. IV 



number of rhopalia is regularly twelve; four perradial and eight 

 adradial. There are no ocelli. There are five subrectangular, nearly 

 straight marginal lappets between each pair of sense organs; the two 

 lappets adjacent to the rhopalia are only half as wide as the other 

 lappets. The mouth-arm disk arises from the center of the umbrella 

 and is usually about three-fourths as long as the umbrella radius, but 

 sometimes a specimen is taken in which the arms are much longer, 

 approximating those of C. xamachana; in frondosa the arms bifurcate 

 distally, giving rise to numerous short, pinnate branches from the 

 oral side. The many frilled mouths are found only on the lower or 

 oral side of the arms, the upper sides of the arms being smooth. 

 There is no central mouth-opening in the adult, but Louis Agassiz 

 discovered that the ephyra stage of frondosa does have a central 

 mouth aperture. There are 30 to 40 small, flat, leaf-like, expanded 

 vesicles expanded between the mouths. There are four small, round, 

 subgenital pits placed interradially. There are four separate, invagi- 

 nated genital sacs which project into the stomach cavity. The axial 

 ducts of the eight oral arms open into the central stomach and 24 

 radial canals extend from the stomach into the subumbrella, 12 pass- 

 ing to the rhopalia, and 12 are intermediate in position; all 24 com- 

 municate with one another by means of numerous anastomosing 

 branches. 

 References: Medusa frondosa Pallas, Spicilegia Zoolog. fasc. 10, 



pp. 29, 30, pi. 2, figs. 1 to 3, 1774.— Gmelin, in Linne, Syst. Nat. 



t. I, pt. 6, p. 3157, 1788.— Bosc, Hist Nat. d. Vers, t. 2, p. 170, 



1802. 



Cassiopea frondosa Lamarck, Hist. Nat. Anim. sans Vert, tome II, 

 p. 512, 1816. — Eschscholtz, Syst. der Acalephen, p. 43, 1829. — 

 Tilesius, Acad. Caes. Leop. Nova Acta, torn. 15, pp. 263, 278, 

 tab. 72, figs. 1-5, 1834.— Lesson, Zooph. Acaleph., p. 405, 1843.— 

 H. Milne Edwards, in Cuvier's Regne Anim. Zooph., pi. 51, 

 fig. 3, 1849. — Perkins, Yearbook, Carnegie Inst. Washington, 

 no. 4, p. 115, 1906 ; Bull. 102, Carnegie Inst. Washington, p. 152, 

 pi. 4, 1908. 



Cassiopea pallasii Peron and Lesueur, Ann. Mus. Hist. Nat., Paris, 

 tome 14, p. 357, no. 85, 1808. 



Polyclonia frondosa L. Agassiz, Contrib. Nat. Hist. U. S., vol. Ill, 

 pis. 13, 13a, 1860 ; ibid, vol. IV, p. 139, p. 152, pi. 4, 1862.— A. 

 Agassiz, N. Amer. Acaleph., p. 41, 1865 ; Nature, vol. 24, p. 509, 



