RHIZOSTOM.E — VERSURA. 



687 



the 4 perradial canals. There is no true ring-canal, although all 8 of the radial-canals are 

 placed in communication one with another by a marginal zone of anastomosing vessels which 

 extend into the lappets. There are no radial-muscles in the suhumbrella, hut there are 2 

 separate concentric ring-muscles, which are further divided into 8 sectors, the lines of separa- 

 tion being in the radii ot the 8 radial-canals. The outer zone of ring-muscles lies close to the 

 bases of the marginal lappets. The inner zone is not a true circle but is widest in the 4 interradii 

 and narrowest in the 4 perradial lines. The gonads and canal-system appear to be reddish. 



This medusa is described by Maas from a single specimen found in the Malay Archi- 

 pelago by the Siboga expedition. It may be identical with the Fersura briefly described by 

 Goette, 1886 (Sitzungsber. Akad. Wissen. Berlin, jahrg. 1886, p. 837), from the east coast 

 of Africa. Maas gives a detailed description of the medusa. The species is distinguished 

 by its prominent velar lappets, its verv thin, delicately formed bell and mouth-arms, and the 

 furrowed surface of its exumbrella. 



Versura maasi, sp. nov. 



Named in honor of Prof. Dr. Otto Maas in recognition of his notable researches upon 

 medusae. 



Bell 90 mm. wide, flatter than a hemisphere and evenly rounded. Exumbrella finely 

 granular, without furrows. Gelatinous substance fairly thick but not very rigid. 8 rhopalia, 

 each with a pigment mass and an exumbrella pit with smooth floor. 112 marginal lappets. 



M 



Fig. 416. — Veriura maasii. Drawn by the author, from a specimen obtained by the U. S. 

 Fisheries Bureau steamer Albatross in the Philippine Islands. 



.A, oral view showing 6 of the mouth-arms cut off close to the arm-disk. In the lower sector the 

 circular muscles are removed exposing the canal-system. B, magnified view of one of 

 the clubs from between mouths of the mouth-arms. C, mouth-arm seen from the 

 outer (abaxial) side. D, exumbrella view of one of the marginal sense-organs. 



The i6 rhopalar lappets are only slightly narrower than the velar lappets. There are usually 

 12 velar lappets in each octant. The outer edges of all lappets are bluntly rounded. The 

 arm-disk is five-ninths as wide as the bell-diameter in the perradius where it arises from the 

 suhumbrella, but is only one-fourth as wide as the bell-diameter at the level of the origin of the 

 8 mouth-arms. The 4 interradial subgenital ostia are twice as wide as the perradial arm-disk 

 columns. There is a wide unitary subgenital porticus. The 8 mouth-arms are each one- 

 third as wide as the bell-diameter. The 3-winged lower part of each arm is somewhat more 

 than twice as long as the unbranched proximal shaft of the arm. The 2 lateral, outer wings 

 of each arm are deeply cleft (fig. 416, c). There are a very few, small, club-like appendages 

 (fig. b) among the mouths of the mouth-arms, but the center of the mouth-arm disk bears 

 a great number of clubs. These clubs are laterally flattened, the largest being only 10 mm. 

 long and besprinkled with nematoc\st-bearing wans which are especially numerous upon 



