TRACHYMEDUS^E — HOMCEONEMA. 



385 



Homoeonema typicum Maas. 



Homvonema typicum, Maas, .897, Mem. Mus. Comp. Zool.it Harvard College, vol. 23, p. . M, taf 3, fign 1 3 



( >) TrachvnrJhngivemrh (young medusa ?), Maas, ,893, Ergeb. der Plankton Exped., Bd. %, , K.c, p. I», taf , fig. 7. 



N.» Rk.Loncma typicum, Agass.z, A., and Mavo, .902, Mem. Mus. Comp. Zool. at Harvard College, vol. ,6, p. 15a, plate J, 

 fies 21, 22.-Bigelow, 1904, Bull. Mus. Comp. Zool. Harvard College, vol.39, p. 256. 



CW.JL >«iceum, Vanhofpen, ,902, Wissen. Ergeb. deutsch. Tiefsee Expedition Dampfer < £*J^' * ^" 'l^ 

 taf. 9, fig. .; taf. .2, fign. 39-42.— Brownf., .906, Trans. L.nnean Soc. London, ser. 2, Zool., vol 10, , p. yz. B.ge 

 low H B., .909, Mem. Mus. Comp. Zool. at Harvard College, vol. 37, P- '33. pl»" h 6g s - 4> 5i P'^ 45. 6g- »■ 



CM™™' »>/>•««, Maas, 1905, Craspedoten Medusen der S/ie^ Expedition, Monog. 10, p. 53- " f - '°> &«■>• 62 - & 5- 



Bell hio-her than a hemisphere, thin but rigid walls, evenly rounded above 45 mm. 



230. 



Fig. »o.-H»m»«« (C/.i.« m <i) typicum, after Maas, in Hydromedusen Siboga Expedition. 

 Fig. z V .-"Colobonema" sericeum, after Vanhoffen, in Tiefsee Expedition Valdw.a. 



there are only 8 tentacles, one at the base of each radial-canal. The next to develop are 8 

 adradial tentacles close by the sides of 4 alternate, radial tentacles Then 8 more adradial 

 tentacles appear by the sides of the remaining 4 radial tentacles. Then 4 interradial tentacles 

 develop 90° apart, and finally 4 more interradial tentacles grow out in the rema.n.ng spaces. 

 Thus the medusa goes through 5 stages as follows: 



4 interradial= 32. 



This peculiar order of development of the tentacles has been observed by both Vanhoffen, 

 Bieelow, and Maas. Lithocysts ( ? ) 



The velum and the circular muscles of the subumbrella are well-developed I here are 

 8 short radial-canals and a narrow, simple ring-canal. The manubnum is one-third to three- 

 fourths as long as bell-height and has 4 sharply-pointed lips. 8 narrow, spindle-shaped gonads, 

 with blunt ends near the edge of the stomach and pointed ends near the circu ar canal. When 

 young they are found on the outer two-thirds of the radial-canals, but usually extend toward 

 the periphery of the stomach so as to cover about three-fourths of the radial-canals, leaving 

 both ends free. Color brilliantly iridescent and transparent (Vanhoffen, B.gelow) but in the 

 preserved medusa studied by Maas the stomach, canals, and gonads were light-brown. 



Maas appears to have first described this medusa from great depths off the Pacific coast of 

 Central America and later from depths of 210 to 77 o fathoms from the Malay Archipelago. 

 Vanhoffen records it from the west coast of Africa from Sierra Leone southward to 42 a. lat. 

 from depths of 115 to 1,500 fathoms. . 



Vanhoffen, 1002, presents beautiful figures of the medusa which agree with the description 

 of Maas, excepting that the gonads are upon the outer two-thirds of the radial-canals and the 

 stomach is shorter than the depth of the bell-cavity. These same conditions characterize the 

 original « Homvonema typicum" described by Maas, 1897, from the Pacific coast of Central 



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