446 



MEDUS-ffi OF THE WORLD. 



The velum is simple, annular, and provided with powerful circular muscles. The mouth 

 is a simple annular opening at the thick lenticular center of the subumbrella. 



28 simple, unilocular saccules project downward into the bell-cavity at the stomach- 

 margin, one in each antimere. These bag-like protrusions thus alternate with the radii of the 

 tentacles and contain the genital organs, the specimen being a male. The marginal ring-canal, 

 or "festoon-canal," is very wide. It extends down the sides of the peronial strand on either 

 side of the insertion of each tentacle and along the margin of each lappet. It is thus broken 

 up into 28 loops, one in each antimere. 



The gelatinous substance of the bell is hyaline. The tentacles, gonads, stomach, and 

 festoon-canal are milky — slightly brown in formalin. 



The medusa is probably immature, for half of its tentacles are of small size and belong 

 apparently to a set which is in process of development. The specimen is perfect and is well 

 preserved in formalin. 



Fig. 298A. — Pegantha clara. A, side view. B, oral view of part of bell-margin showing velum (V), otoporpie (op), and 

 insertions of long set of tentacles (ti). C, oral view of part of bell-margin, showing genital saccules of subum- 

 brella (go), otoporpae (op), peronial strands, (p), marginal festoon-canal (ric), and tentacles (t). 



It is distinguished from P. cyanostylis by having only 2 to 5 sense-clubs upon each lappet, 

 whereas in P. cyanostylis there are 25 or 30. It is distinguished from P. punctata by iis 

 long, slender tentacles. 



It is due to the generous permission of Prof. Robert P. Bigelow that I am permitted not 

 only to study the single specimen of this rare medusa, but also to copy the excellent figures 

 which he made of it soon after its capture by the U. S. Fish Commission steamer Fish Hawk 

 on the surface, near the borders of the Gulf Stream, off Woods Hole, Massachusetts, in Sep- 

 tember, 1899, Station No. 7068. 



Pegantha smaragdina H. B. Bigelow. 



Pegantha smaragdina, Bigelow, H.B., 1909, Mem. Museum Comp. Zool. Harvard College, vol. 37, p. 90, plates 14, 19, 22-26. 



The resemblances between this medusa and R. P. Bigelow's P. clara are so close that the 

 two may prove to be identical; in which case the form should be called P. clara, this name 

 having a publication precedence of a few weeks over P. smaragdina. P. smaragdina appears 

 to be distinguished from P. clara, however, by its flatter, less doubly convex bell and by its 

 decided lemon-yellow color. 



The bell in P. smaragdina is J7, mm. wide, 15 mm. high, being low, flat, and without 

 sculpturing. 28 to 34 tentacles and lappets. Lappets quadrate about as long as broad, as in 

 P. clara. Tentacles stiff, tapering, nearly as long as bell-diameter, as in P. clara. Usually 



