332 



MEDUS.E OF THE WOULD. 



iEquorea tenuis. 



Rhegmatodes tenuis, A. Agassiz in L. Agassiz's, 1862, Cont. Nat. Hist. U. S, vol. 4, p. 361.— Agassiz, A., 1865, North Amer. 

 Acal., p. 95, figs. 136-138.— Verrill, 1873, Report Commiss. Fish and Fisheries for 1871-72, pp. 454, 729.— Haeckel, 

 1879, Syst. der Medusen, p. 223.— Harcitt, 1901, American Naturalist, vol. 35, p. 591, 58; Ibid., 1902, vol. 36, p. 

 553; 1904, Bull. U. S. Bureau of Fisheries, vol. 24, p. 51, I fig.; 1905, Biological Bulletin Marine Lab. Woods Hole, 

 vol. 9, p. 368, 14 figs, in text (variations). — Nutting, 1901, Bull. U. S. Fish Commission, vol. 19, p. 383, fig. 105, a, b. 



Adult medusa. — Bell 80 to 100 mm. in diameter and 3 or 4 times as broad as high. 

 Gelatinous substance thick at apical pole, gradually becoming thinner approaching the margin. 

 Cavity of subumbrella shallow. 48 to 90 long, slender tentacles, which are about twice or 

 three times as numerous as the radial-canals. The long tentacles have large, conical, hollow 

 bases. Besides these long tentacles, there are about 200 to 250 small rudimentary tentacles. 

 Excretion papillae, or "spurs," are found at the bases of most of the large tentacles upon 

 the subumbrella side of the circular canal. 48 to 90 lithocysts, each containing 2 concretions. 

 Velum well developed. About 241032 long, straight radial-canals extend from periphery of 



stomach to circular canal. 

 Stomach flat and funnel- 

 shaped, about one-fifth 

 as wide as diameter of 

 bell. The mouth is a 

 small opening surrounded 

 by very minute lappets or 

 folds. The gonads are 

 lineaT and are situated 

 upon nearly the whole 

 length of radial -canals, 

 not quite reaching the 

 circular canal. 



This species is abun- 

 dant in Buzzard's Bay, 

 Massachusetts, and in the 

 eastern part of Long 

 Island Sound in Septem- 

 ber, but it is far commoner 

 in some years than in 

 others. 



Young specimens of a diameter of 40 to 50 mm. have 16 to 24 radial tubes. 

 Hargitt, 1905, describes and figures many departures of this medusa from the normal, 

 and finds that the radial-canals, gonads, and lithocysts are all very variable both in form, num- 

 ber, and position. The radial-canals often display anastomoses, forkings, and loops, as in 

 other species of JEquorea. 



jEquorea globosa Eschscholtz. 



JEquorea globosa, Eschscholtz, 1829, Syst. der Acal., p. no, taf. 10, fig. 2. — Maas, 1905, Craspedoten Medusen der Siboga 

 Expedition, Monog. 10, p. 43, taf. 8, fign. 48-50. — Bigelow, H. B., 1909, Mem. Mus. Comp. Zool. at Harvard College, 

 vol. 37, p. 173- 



Rhegmalodes globosa, Haeckel, 1879, Syst. der Medusen, p. 222. 



The disk is about 20 to 40 mm. wide and the gelatinous substance is very thick, so that 

 the exumbrella is almost hemispherical, or higher, with bulging sides; while the subumbrella 

 is almost flat and the bell-cavity very shallow. There are about 50 tentacles, 50 radial-canals, 

 and the same number of lips. The stomach is about half as wide as the diameter of the 

 disk. The well-developed tentacles are slender, tapering, and less than bell-radius in length. 

 They have large basal bulbs which are urn-shaped, being wider below than at bell-margin. 

 The lithocysts and tentacle rudiments are each about twice as numerous as the tentacles and 

 are quite regularly spaced around the margin. Velum narrow. Radial-canals straight, simple, 

 and narrow. The stomach lacks a peduncle and the lips are pointed and may close the oral 

 opening. The thin, linear gonads are developed upon almost the entire lengths of both 

 sides of each radial-canal. Gonads and radial-canals greenish-gray. 



Fig. 191. — Mquorea tenuis, after A. Agassiz, in North American Acalepha?. 

 Oral view, natural size. 



