Klll/i iSTHM.K rASSIul'i: \. tl II 



I his medusa \v;is found in lare swarms In Keller on the shallow coral Hats ol the southern 

 parts of the Red Sea. Ir dirrers from i lie M pical (.. anJromeJa in the thick-rimmed sucker ot 

 the exumbrella, and die long, laterally compressed arms. Keller describes it in detail with JMMX! 

 figures. In common wiih other C'assiopmke it lies upon the boMoni with its oral surface 

 uppermost. Keller draws comparisons between its habits and structure and those ot actimans, 

 etc. This medusa is probably only a local variety of ('.. undrrniu-Jn, but the thick, sucker- 

 like disk at the middle of the exumbrella appears to distinguish it. 



Cassiopea xamachana R. P. Bigelow. 



Plate 'MI, ti | 'o X; plates 70 and 71; plate 72, tin- *-ven lo.'.-r h 



C.iixivfx-ii \nni(i< htin,!, Hi>. new. K. P., iSij2, Zooloi;. An/eiqrr, Bd . i ^, p. 212; fohns Hopl.ins I'niMTMty Circular*. 1X92, 

 MI|. ll, pp. 71, 84; 189^, Journal Institute of Jamaica, vul. i, p. ',01, i plate; 1900, Memoirs Boston Soc. Nat. Hi ., M'|. ?, 

 NIL 6. p. 191, hi; . \ in I.. pl.iti ;i in ;X, 66 figs. PI:RKINS, 1905. Year Book of the Carnegie Institution, No. 4, p. i iX. 

 Publication, NCI. 102, p. 150, plate 4. MAIKK, ii|O', Year Rook of tin- Carnegie Institution, Ni>. 4, p. 117; Publuation 

 nf lln- Carnegie In^itution, No. 4-, (12 pp. (rlutlimical puhation); 1907, Year Itook ('.ini'-L-i'' lir ritufmn. Nn. fi, p. 121; 

 [hi<t., i<)oX, No. 7, p. i;;. MA*V, i>to\. Si \ pli-nui ,|IIMTI I-T A//Ky,i Kxpedition, Mmi"'. ii. p. 40. STOCKMU>, lo~, 

 ^ i .11 Hunk t'.iincL'i'' In tiuitinii "t \\ .1- liiiifi'iii, N". d. p. MI) (regeneration)] Ihid., No. 7, 1908, p. i;o. Papers from 

 TorhitM J.alioi.it.in i if t'arni'Kii- IriMitutinn ol \\aslnni;!. m, vol. 2. p. 61, fit;!.. l-2!; Journal of KxpiTinii ntal X,!-.|nf\. 

 M|Oj, vi ii. Ii, p. 4;;, S hr . /i i i N t , t .. ii)O^. [oiirna! Kxprrimi-nta! Zoology j "1. S, p. 2l;, 4 ti' \t-hi; . (n-t;i-n' 

 DAHLGREN AND KKPHIR, 1908, Text-Book of Principles of Animal Histology, p. 88, fi ' NUvin. 



1908, Papers, from tin-- 'I'oriur. i l..ilat<>i\ of the Carnegie In 'itntnui ot Wa-.liini;ton Puhln ,nion. \... 102. p. 1 1 -, (the 

 cause of rhytlinti! .il pnl .111011 ); Popular Scinui- Monthh. Mil. 7;, pp. 4X1 4X-, 4 hi; 1 .; 1909, Rrport of ?th Interna- 

 tiona! Xooloi;ii.al (.'ont^n-'s, 4 |>p. Harvey 1909, Year Book of the Carnepie Institution ot Washington] No. S, p. 119. 



Cassiopea frondosa, FKWKV-. 1^X2, Hull. Museum Comp. Zool. at Harvard College, vol. 9, p. 254, plate I, figs. 7-19; plate 2, 

 figs, i, 2; plate 3, figs. 1-3, 9, ioj Ibid., 1883, p. So, plate i, fig. 16. 



The disk is usually about 150 mm. in diameter, although Bigelow records one from 

 Jamaica 240 mm. wide. It is flat and with rounded edges. There is a well-marked con- 

 cavity at the middle of the exumbrella, the diameter of which is about equal to the disk- 

 radius. It enables the medusa to cling firmly to any smooth surface as by a sucker. 



The number of the marginal sense-organs ranges from 1 1 to 23, although there are usu.ilh 

 about 16. For example, in 25 medusa taken at random and ranging in si/.e trom 23 to 149 

 mm., one had 13 marginal sense-organs, i had 14, i bad 15, 12 had 16. 5 had 17, i had 18, 

 1 had 19, 2 had 2O. I have seen one medusa with 1 1 and one with 23 sense-organs. The 

 number is independent of the si/.e of medusa, being determined at time of strobih/.ation. 



The sense-organs are short, blunt, and club-shaped, and are set within niches protected 

 above by a shelf-like membrane spanning the cleft between the adjacent lappets. There is 

 no exumbrella pit above the club. Kach sense-organ contains a terminal mass of entodermal 

 crystals and an aboral cup-shaped cctodermal ocellus having reddish-brown pigment. I here 

 are 5 short, blunt, rounded lappets between each successive pair <>t st us. .ugans; the 2 lappets 

 adjacent to the sense-organs are only about half as wide as the others. The mouth-arm disk, 

 which projects as a flat plate from the center of the subumbrella, is only about two-thirds as 

 wide as the disk-radius. 4 pairs of adradial mouth-arms arise from this disk. Each of these 

 8 mouth-arms is about 1.25 times as long as radius of bell and projects somewhat beyond 

 bell-margin. These mouth-arms are triangular in cross-section, their aboral surface bem 

 broad and flat; they each give rise to 10 to 15 alternate, primary branches, which in turn 

 give rise to secondary blanches. These branches are commonly longer than in C. fronJosa 

 and are also longer and stouter than in (',. ,in.li',tn,-Ja Eschscholt/. and more slender and have 

 more primary branches than in (.'. polypoi.L* Keller. In the axil of each piimai\ branch ot 

 the mouth-arms is a single, flat, ribbon-like filament, which \aiies in length with the size of 

 the adjacent branch. There are also 5 to 13 large, ribbon-shaped filaments upon the oral 

 surface of the mouth-arm disk. The largest filament is at the center and is fully one-tonnli 

 as lon<; as the bell-diameter. The filaments decrease successively in length out over the 

 mouth-arms; those at the tips of the arms being only about one-seventh as long as those at 

 the center. In addition to the filaments there are numerous short club-shaped, nematocyst- 

 bearing vesicles scattered among the mouths. 



The mouths are found upon the oial (uppermost as the medusa lies upon the bottom) 

 sides of the primary and secondary branches of the mouth-arms, and to some extent upon 

 the oral sides of the 8 basal trunks of the arms. There are no mouths at the center ol the 



