154 THE MEDUSAE. 



PMalium duodecimalis A. Agassiz. 



Eucheilota duodecimalis A. Agassiz, '62, p. 353; '65, p. 75, figs. 106, 107, 107a; Hargitt, 



: 05^ p. 46, pi. 4, fig. S. 

 Phialium duodecimale Haeckel, '79, p. 180; Fewkes, '82% p. 297, pi. 1, figs. 17-21. 

 Phialium dodecasema Haeckel, '79, p. 181. 



Plate 6, Fig. 4; Plate 38, Figs. J^, 5. 



Acapulco Harbor ; surface ; many specimens, 1 to 2 mm. in diameter. 



It has been my good fortune to have access to a large series of P. 

 duodecimalis, from Newport, R. I., for comparison with the present speci- 

 mens, and, as in the case of Phialidlum discoida, I have been unable to find 

 that there are any constant differences to separate the two. The Pacific 

 series, none of which are full grown, agree closely in general form, and in 

 the size and shape of the gonads, with Atlantic specimens of about the 

 same size. 



The most important specific characters are to be looked for on the 

 marginal organs. In each specimen there are four radial tentacles, with 

 swollen conical basal bulbs flanked with from one to four pairs of cirri ; and 

 twelve otocysts, three per quadrant, each containing a single large otolith ex- 

 actly as is figured for P. duodecimalis by A. Agassiz ('65, fig. 107) and by Fewkes 

 ('82*", figs. 17-21). There are no rudimentary tentacular swellings on the 

 margin in any of the specimens. Such structures, alternating with the oto- 

 cysts, have, it is true, been recorded, but not figured, by Fewkes ('82'') for 

 very large specimens from Newport ; but inasmuch as Hargitt (: 05'') has not 

 observed any, but states expressly that there are only four tentacles, and 

 since the writer has never seen any in the numerous large specimens from 

 the Atlantic coast of the United States which he has examined, it is probable 

 that the specimens with more than four developed tentacles, which Fewkes 

 records, in reality belonged to Eucheilota ventricularis, a species which might 

 easily be confused with the present if the otocysts were not counted. 



In all the specimens gonads were developed, but in none were they of 

 such large size as they finally become. In some of the Newport specimens 

 they are so swollen that they fill almost the entire bell. 



The Medusae are entirely colorless. 



So far as I have been able to learn, the only species known from the 

 Indo-Pacific region which resembles this species is the Mitrocomium assiniile 

 described by Browne (: 05'', p. 137, i^l. 1, fig. 3) from Ceylon. Unfortunately 



