HYDROMEDUSAE, SIPHONOPHORES, AND CTENOPHORES. 317 



(pi. 43, fig. 6) described in detail elsewhere (1912, p. 257). These are 

 restricted to the central two-thirds of the disk, arranged in rows 

 alternating with the radial canals ; 4 to 15 papillae in each row. In 

 the region of the manubrium they are represented by low rounded 

 knobs ; 16 in one specimen. 



Haeckel's (1879) records for the genus (-\-Zygocannota-\-Zygo- 

 cannula) are from New Guinea, and straits of Sunda; the " Siboga " 

 specimens (Maas, 1905) from Malayan waters. 



Order TRACHOMEDUSAE. 



Family PETASIDAE Haeckel, 1879. Sens. Em. Browne (1904) ; 

 Bigelow (1909a, 1915&). 



This family corresponds to the 01indiadae-|-subfamily Petasinae 

 of Mayer (1910). Mayer leaves the relationships between his two 

 groups open; and he adds to the latter Craspedacusta, both Goto 

 (1903) and Browne (1904) having maintained that the affinities of 

 the latter are with such genera as Olindias and Gonionemus. 



I follow Browne (1904) in dividing this family into two subfam- 

 ilies, Olindiinae with the otocysts in capsules, Petasinae in which they 

 are free clubs (1909a, 19156). 



Subfamily Olindiinae. 



Genus OLINDIAS F. Miiller, 1861. 



The genus Olindias is known from the Indo-Pacific, by two forms 

 races or species, O. phosphorica var. malayensis Maas, and O. singu- 

 laris Browne (1904). In my memoir on the "Albatross" Eastern 

 Pacific Medusae (Bigelow 1909a, p. 109) and in Mayer's (1910) 

 Monograph, the characters of members of the genus from various 

 parts of the world will be found tabulated. The general conclusion, 

 as Mayer points out, is that the various Atlantic representatives are 

 at most geographic races of one species, phosphorica. The case of 

 the two Indo-Pacific forms is still obscure. With the evidence avail- 

 able at the time, I recognized both, singularis with usually one, phos- 

 phorica with usually or always 2 otocysts at the base of each primary 

 tentacle. The Mangareva specimens had one otocyst at the base of 

 most, two at the bases of a few, primary tentacles. Hence they were 

 associated with singularis. In the Philippine specimens also single 

 otocysts predominate largely over paired. As pointed out elsewhere 

 (Bigelow, 1909a) single antedates paired otocyst in ontogeny in 

 Olindias. In the Atlantic specimens of the genus paired otocysts are 

 developed at the base of a primary tentacle very soon after the latter 

 is formed. In Indo-Pacific representatives single otocysts may persist, 



