SYSTEMATIC AND 



33 



SYSTEMATIC AND BIOLOGICAL ACCOUNT 



CHONDROPHORA 



Porpita Lamarck, 1801 



Forty years ago Bigelow (191 16) reviewed the question of generic and specific limits in Porpitidae. 

 I do not think further progress will be made by any survey of literature, but only by the fresh examina- 

 tion of all growth stages from both Atlantic and Pacific. On a priori grounds it seems unlikely that 

 species of these surface animals from tropical and sub-tropical waters would be isolated in one or 

 other ocean — that is, if our knowledge of distribution of other siphonophores, and if Sewell's (1948) 

 views on transportation of planktonic copepods are any guide. Haeckel recognized no less than six 

 genera and twenty species of Porpitids. Bigelow regarded many of Haeckel's forms as growth stages 

 and provisionally recognized two genera and five species. Bigelow considered five points in the anatomy 

 of Porpita: (1) the tubercles on the upper surface of the disc, (2) the arrangement of the stigmata, 

 (3) comparative width of the limbus, (4) radial or branching arrangement of the canals of the limbus, 

 and (5) the number of stalked tentacular nematocyst clusters on the tentacles, and from a study of 

 these anatomical points, he came to the conclusion that an Atlantic form Porpita umbella could be 

 distinguished from a Pacific form P. pacifica; but he doubted if a Pacific and Atlantic species of 

 Porpema — the only other genus he recognized — could be distinguished. 



I am inclined to think that there are only two Porpitids, Porpita porpita (L.) and Porpema prunella 

 (Haeckel, 18886), and that one genus Porpita is enough to contain them. 



Porpita porpita (Linne), 1758. 



(Synonymy in Bigelow, 191 ib, p. 353.) 



Porpita umbella (O. F. Miiller), 1776. 

 (Synonymy in Bigelow, 191 ib, p. 352.) 



Porpita pacifica Lesson, 1826. 

 (Synonymy in Bigelow, 19116, p. 333.) 



