TRACHYMEDUS.E — GONIONKMUS. 341 



The Olindiadae form a well-defined group of shallow-water, bottom-living medusae, the 

 species of which have, apparently, quite similar habits each to each. The medusa; are as a 

 whole widely distributed, but each species appears to be quite restricted and only locally 

 abundant. 



The exumbrella tentacles are connected with the ring-canal by entodermal roots and 

 project more or less stiffly from the sides of the bell above the margin. These tentacles are 

 always provided with aboral, disk-like, adhesive pads near their outer ends. Besides the 

 exumbrella set, tentacles may arise from the velar margin. These are quite flexible, hollow, and 

 may or may not be provided with adhesive pads. They are armed with rings or helices of 

 ectodermal, nematocyst-bearing ridges. 



The gonads are developed exclusively upon the walls of the radial-canals in the form of 

 linear or sac-like folds. The gonad usually becomes longer than the portion of the canal upon 

 which it is developed, and it is then reflected from side to side in a sinusoidal curve. Later 

 hernia-like outgrowths may develop over the surface of the gonad and it thus acquires a 

 papilliform aspect. 



The development of Gonionemus has been studied by Perkins, 1903, but we know nothing 

 of the manner in which the medusa arises from the hydroid. The growth of the medusa 

 of Olindias was studied by Mayer, 1904, but its polyp-stage remains unknown. 



The genus Mczotias OstrooumofF, 1896, appears to have marginal tentacles only, and 

 apparently these lack adhesive disks, or at least such are not mentioned by OstrooumofF. I 

 have, therefore, considered this genus to be one of the Petasidae, not of the Olindiadae. 



The Olindiadae are, however, very closely related to the Petasidae, and I am much 

 inclined to follow Bigelow, 1909, and unite the Olindiadae and Petasidae under one family, 

 calling it Petasidae. I am deterred from taking this step only because our knowledge of the 

 Petasidae is, with the exception of the genus Gossea, so apochryphal that I hesitate to classify 

 these medusae excepting in a group of their own from which they may be readily removed 

 should future studies reveal them to science once again. As Bigelow shows there is no doubt 

 of the close relationship between Gonionemus and Gossea. 



A synopsis of the genera of the Olindiadae follows: 



Gonionemus A. Agassiz, 1862, 1865. The tentacles all project from the sides of the exumbrella above the margin and are all 



provided with adhesive disks. Lithocysts external. 4 radial-canals. No centripetal canals. 

 Cubaia Mayer, 1894. Similar to' Gonionemus, but with two sorts of tentacles, one set arising from the bell-margin, the other 



set projecting from the sides of the exumbrella. Lithocysts external. 

 Valhntinia Browne, 1902. Similar to Cubaia, but with lithocysts adjacent to the ring-canal and inclosed on the inner side above 



the velum. (This is probably only a young Olindias). 

 Olindias F. MOller, 1861. Similar to Valhntinia, but with blindly-ending, centripetal diverticula from the ring-canal. 

 Olindioides Goto, 1903. Similar to Olindias but with 6 radial-canals (2 simple and 2 bifurcated). 6 gonads. Exumbrella 



tentacles projecting at various levels. 4 lips. 



Genus GONIONEMUS A. Agassiz, 1862. 



Gonionemus, A. Agassiz in L. Agassiz, 1862, Cont. Nat. Hist. U.S., vol. 4, p. 530; 1865, North Amer. Acal., p. 128— Murbach, 

 1895, Journal Morphol., vol. II, p. 2.— Agassiz and Mayer, 1899, Bull. Mus. Comp. Zool. at Harvard College, vol. 

 32, p. 164. — Mayer, 1904, Mem. Nat. Sci. Museum Brooklyn Inst. Arts and Sci., vol. 1, p. 19. — Browne, 1904, Fauna 

 and Geog. Maldive and Laccadive Archipelagoes, vol. 2, p. 738; 1905, Report Pearl Oyster Fisheries, Gulf of Manaar, 

 p. 149. — Hargitt, 1904, Biol. Bulletin Woods Hole, vol. 6, p. 241.' — Bigelow, H. B., 1909, Mem. Mus. Comp. Zool. at 

 Harvard College, vol. 37, p. 105. 



Gonvncma, Haeckel, 1879, Syst. der Medusen, p. 146. 



Gomonema, Perkins, 1902, Johns Hopkins Univ. Circ, May, 1902; 1903, Proc. Acad. Nat. Sci. Philadelphia, vol. 54, p. 750 — 

 Goto, 1903, Mark Anniversary Volume, pp. 12, 19, 20. 



The type species is Gonionemus vertens A. Agassiz, 1862, 1865; from Puget Sound, 

 Pacific coast of North America. 



Haeckel introduced the spelling "Gonynema," and Perkins proposed to change the name 

 to "Gonionema," in an endeavor to correct, or improve upon, the original termination proposed 

 by Agassiz. It appears to me that in the case of generic names we should retain the original 

 spelling proposed by the author of the genus, regarding the name as a mere combination of 

 letters which may or may not have significance or meaning. The strongest argument in favor 

 of this view appears when we consider that if we are to correct the spelling of the generic 

 names in zoology, a surprisingly large proportion of now familiar names must be considerably 

 amended. 



