SCYPHOMEDUSAE COLLECTED BY STEAMER " ALBATROSS." 227 



the center and gives off side branches in the tissue between the win- 

 dows to the mouths. These side branches are joined one to another 

 by longitudinal canals near the frilled mouth (see fig. 22, B). 



There are numerous appendages upon the mouth-arms arising be- 

 tween the mouths. Those near the lower pointed ends of the mouth- 

 arms are large, spindle-shaped, more or less triangular in cross- 

 section and taper to pointed ends. Those arising higher up are more 

 slender, and above these there are mere threadlike filaments. The 

 appendages are usually 70 to 100 mm. long, and the large ones con- 

 tain an axial duct. The general color of the medusa in formalin is 

 milky-gray, the mouths and gonads being darker than other parts. 



Genus THYSANOSTOMA L. Agassiz, 1862. 



Thysanosioma Agassiz, 1862, Contr. Nat. Hist. U. S., vol. 4, p. 153. — Mayer, 

 1910, Medusae of the World, vol. 3, p. 691. 

 Generic Characters. — Rhizostomata lorifera having mouth-arms 

 bearing three rows of frilled mouths from base to lower end, without 

 a terminal club. Among characters of minor importance, the four 

 interradial, subgenital ostia are wider than the perradial columns 

 between them. There are eight rhopalar canals and a ring canal 

 which gives off a network of vessels on both its inner and outer sides. 

 This network connects with all the radial canals and also at numerous 

 points with the central stomach. The well-developed circular muscles 

 are only partially interrupted in the eight principal radii. There is 

 a small, shallow, exumbrella pit above each sense organ, and there 

 are no furrows in the floor of the pit. The only difference between 

 this genus and the closely allied Lorifera is that the frilled mouths 

 are developed even to the tips of the lower ends of the mouth-arm 

 and there is no terminal club, whereas Lorifera has a naked terminal 

 club. 



THYSANOSTOMA THYSANURA Haeckel. 



(?) Rhizostoma brachyura Lesson, R. P., 1829, Voyage de la Coquille, 

 Zoophyt., vol. 2, p. 153 ; 1830, Centurie Zoologique, p. 227, pi. 80. 



Thysanostoma Agassiz, 1862, Contr. Nat. Hist. U. S., vol. 4, p. 153, figs. 

 1-9.— Mayeb, 1910, Medusae of the World, vol. 3, p. 692, fig. 420. 



The dimensions, in millimeters, of a specimen (Cat. No. 27929, 

 U.S.N.M.) obtained at Mindanao, Philippine Islands, by the United 

 States Bureau of Fisheries steamer Albatross are as follows: Bell, 

 100 wide; perradial diameter of arm-disk, 74; diameter of arm-disk 

 at level of origin of mouth-arms, 48 ; genital ostium, 40 wide ; mouth- 

 arms, 220 long. 24 wide at widest part, 12 wide at their blunt tips; 

 8 to 12 velar lappets in each octant; filamentary appendages on the 

 arm-disk, 10 to 15 long ; exumbrella finely granular. 



In another large medusa (Cat. No. 27930, U.S.N.M.) f rom Mansalay, 

 Mindoro. Philippine Islands, taken by the Albatross on June 4, 1908, 

 from a depth of 150 feet, the bell is 120 mm. wide and the mouth- 



