254 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.43. 



The structure of the gonads, whether ring-like or not, can not be 

 determined from surface views. I therefore sectioned the middle 

 part of the manubrium in the transverse plane. On such a section 

 it is evident that there are eight distinct sexual masses, the develop- 

 ment of the genital products, in this case spermatozoa, being entirely 

 discontinuous both in the per- and in the interradii. Apparently the 

 gonads become continuous in the interradii at the base of the manu- 

 brium. But I could not determine this absolutely, not wishing to 

 section the whole of this unique specimen. Judging from other 

 Pandeids, such a condition might be expected. Probabh'- here, as in 

 Tiara, the adradial masses are f imdamentall}'- the arms of four inter- 

 radial "horseshoes." In the lower (distal) part of the manubrium 

 the interradial gap becomes broader and broader. The sexual prod- 

 ucts are far developed, if not mature. The sections show no trace of 

 interradial entodermal septa s\ich as Linko ^ described. 



Color. — In the preserved specimen the manubrium and gonads are 

 a faint yellow, otherwise it is colorless. 



The various descriptions of the Atlantic Protiaras are so meager 

 that it is not easy to determine whether or not the present specimen 

 is identical with any of them. It is easily separated from Linko's 

 specimen (P. heroe ?), the only one of which we have adequate knowl- 

 edge, by the structure of gonads and manubrium. According to Linko 

 the gonads are interradial, interrupted in the perradii but not in the 

 interradii, and there are four longitudinal interradial entodermal septa 

 which partially subdivide the cavity of the manubrium in its upper 

 portion. As noted above there are no septa in the Philippine form and 

 its gonads are interrupted in the inter- as well as in the perradii. The 

 other accounts of the gonads in forms with four tentacles are vague. 

 According to Haeckel ^ these organs are perradial, and Hargitt's^ figure 

 shows four perradial swellings in his Protiara hseckeli. But, to illus- 

 trate the um'eliability of surface views as evidence for the location of 

 the gonads of this genus, I need only point out that I would undoubt- 

 edly have described them either as continuous, or as perradial in 

 tropica, had I not studied them on sections. 



A difference which may serve to separate tropica from horealis is 

 the presence of exumbral nematocyst clustei's and of terminal ten- 

 tacular knobs m the latter, and their absence in the former. In both 

 these respects Jiseckeli agrees with tropica, but the account of it is 

 meager and it is doubtful whether it belongs to the family at all. 

 The previous records of the genus are all from north temperate or 

 arctic regions. The discovery of a tropical representative is there- 

 fore especially interesting. 



Type.— C^i. No. 29380, U.S.N.M., from the locality given. 



> Zool. Anzeiger, vol. 25, 1902, p. 162. 



= Pas System der Medusen, 1879. 



s Medusae of ttie Woods Hole Regiou. Hull. L'. S. Bureau of Fislieries, vol. 24, 1905. 



