64 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 53. 



Total length, not accounting for curves, 8 mm. Length of head, 

 including processes and horns, 2.50 mm. Length of trunk, T mm.; 

 diameter, 1.30 mm. Length of egg strings, 1-i mm. 



Color (preserved material), a uniform light 3'ellow. 



{medusaeus, medusa-like, alluding to the anterior processes.) 



Intc7'nal anatomy. — The chitinogen layer of the body wall is 

 somewhat thickened in the second, third, and fourth thorax seg- 

 ments, and also in the anterior end of the fifth segment. "While there 

 are no definite skin glands as in Sarcotrctes^ there are many large 

 conical or funnel-shaped pores through the outer chitin layer in these 

 regions, which communicate with the chitinogen cells and may well 

 serve as excretory ducts (fig. 21). 



Esophagus inclined ventrally to the axis of the head and opening 

 into a stomach which is somewhat unsymmetrical as can be seen from 

 figure 19, which has no convolutions, and which sends out no lateral 

 processes. The ovaries are comparatively short and narrow, while 

 the oviducts are very wide, filling nearly the whole cavity of the 

 trunk (fig. 15). 



The cement glands do not reach the anterior end of the oviducts, 

 and are somewhat flattened dorsoventrally between the latter and 

 the body wall, while the oviducts are a little flattened laterally. 



Iiemarks. — This description is intended to supplement and in a 

 few particulars to correct the one previously given. The former 

 specimen was evidently injured on removing it from the fish. These 

 two specimens were sent still attached to their host and were re- 

 moved uninjured. 



The characters which distinguish the species from Richiardi's 

 hellottii are in the position and arrangement of the frontal processes 

 and the posterior soft horns. In hellottii the frontal processes ex- 

 tend backward on the ventral surface a considerable distance be- 

 yond the base of the head and the soft posterior horns, while there 

 is an additional pair of laminate processes or wings on the sides of 

 the second thorax segment, as Richiardi stated. 



In medusaeus the frontal processes only extend to the anterior 

 margin of the posterior horns, the latter are distinctly on the ccphalo- 

 thorax, and there is nothing on the sides of the second thorax seg- 

 ment (fig. 18). 



Ikloreover, in medusaeus there are no vestigial second maxillae an- 

 terior to the first legs, as noted by Jungerscn for hellottii.'^ 



The species found by Brian on M yctophum aifine and referred to 

 medusaeus appears to be correctly located, as will be seen by com- 

 paring his plate 10, figure 5, with plate 3, figure 15, of the present 

 paper. 



» Vidensk Meddel, fra den Naturh. Foren., vol. 64, 1911, p. 13, fig. 1, text, pi. 2, flg. 27. 



