494 MEDUSAE OF THE WORLD. 



distance toward the apex above the margin. The interradial, adradial, etc., tentacles also 

 project from the sides of the exumbrella but at successively lower levels, nearer the bell- 

 margin. All of the tentacles are joined by peronial strands to the ring-canal. The tentacle 

 bases of the last two cycles bear ocelli. The gastric peduncle is broadly conical and more 

 than half as long as the depth of the subumbrella cavity. The manubrium is short with 4 

 fairly prominent, frilled lips. The gonads are elongate, pendant, and sausage-shaped and con- 

 fined to the gastric peduncle where they are developed in great numbers along the 4 radial- 

 canals. The parts of the radial-canals over the subumbrella are narrow and devoid of side 

 branches. Manubrium, gonads, and tentacles pale yellow, canals yellow, occasionally carmine. 

 Found along the coast of California northward to Monterey and San Francisco, from 19 to 86 

 fathoms. Surface in Oakland Harbor and at Lajolla, California. 



This is one of the largest and most beautiful of the Hydromedusae. 



Ptychogena californica Torrey. 

 Ptychogena californica, Torrey, 1909, Publications University of California, Zool., vol. 6, p. 13, figs. 1 and 2. 



Bell 10 mm. wide, more than half as high as broad. About 48 tentacles, with thickened, 

 compressed bases and slender filaments. 1 to 5 cordyli between every two tentacles. The 

 cordyli mounted on prominent basal-bulbs as in Staurophora. Manubrium shallow, about 

 half as wide as the bell and with large mouth without lobes. Gonads with 12 to 14 folds in 

 the proximal half of each radial-canal. Two specimens off San Diego, California, in a vertical 

 haul from 210 fathoms. Color ( ?) 



Obelia purpurea Torrey. 

 Obclia purpurea, Torrey, 1909, University of California Publications, Zool., vol. 6, p. 20, fig. 6. 



This Obelia medusa is 3 to 4 mm. in diameter and has no to 160 tentacles. Its only 

 distinctive character is the violet-purple color of its tentacle-bulbs and its yellow manubrium, 

 canals, and gonads. It is found off San Diego, California, in winter and summer, at the surface 

 and down to a depth of 160 fathoms. 



Obelia nigrocaulus Hilgendorf. 

 Obelia nigrocaulus, Hilgendorf, 1898, Trans, and Proc. New Zealand Institute, vol. 30, p. 203, plate 17, figs. 1, \a. 



This species is distinguished by the dense black color of the basal parts of the stems. The 

 mid-regions of the stems are brown and the distal branches transparent. Gonosome unknown. 

 Hydrothecae oval, with entire orifices. New Zealand. 



Obelia commissuralis (see page 244). 

 Obelia commissuralis, Norton, 1896, American Monthly Microscop. Journal, vol. 17, p. 291, 12 figs. 



A good account of the anatomy and life-history of the hydroid. 



Obelia bifurca Hincks (see page 254). 



Obelia bifurcata, Thornely, 1908, Journal Linnean Soc. London, Zool, vol. 31, p. 81, plate 9, fig. 2.— Billard, 1906, Expeditions 

 Sci. Travailleur et Talisman, tome 8, p. 168. 



Miss Thornely describes this species from Khor Shinab, Sudanese Red Sea, 10 to 12 

 fathoms. She is the first to observe the gonothecae which are conical and not much larger 

 than the hydrothecae, and are borne upon pedicels with about 5 rings each. The stems of the 

 hydroid are slightly branched. 



Tiaropsis kelseyi. 



Tiaropsidium kelseyi, Torrey, 1909, University of California Publications, Zool., vol. 6, p. 19, fig. 5. 



Bell flatter than a hemisphere, 50 mm. wide. 8 large and about 24 to 40 small, apparently 

 rudimentary tentacles. 8 adradial sense-organs as in other species of Tiaropsis. Manubrium 

 wider than in T . diademata. The gonads are more folded and more curtain-like than in 

 Tiaropsis diademata, and are developed along the entire lengthsof the radial-canals. Color as 



