EUCOPIDiE. 81 



ORTHOPYXIS Agass. 



Orthnpyxi.t AoASS. Cont. Nat. Hist. U. S., IV. pp. 297, 355. 1862. 

 Chitia Lamx (p. p.). BulL Soc. Phil. 1812. 

 ? SUicularia Meyen. Nov. Act., XVI. 1834. 



Orthopyxis poterium Agass. 



Orthopyxis poterium Agass. Cont. Nat. Hist. U. S., IV. pp. 297, 302, Fig. 40 ; p. 355 ; Pis. 28, 29, 

 Figs. 1-5. 1862. 



Massachusetts Bay (Agassiz) ; Nova Scotia (Anticosti Expedition). 

 Cat. No. 125, Naliant, April, 1856, H. J. Clark. Hvclromedusarium. 

 Cat. No. 126, Naliant, June, 1861, A. Agassiz. Ilydrarium. 

 Cat. No. 127, Nahant, July, 1861, A. Agassiz. Hydrarium. 

 Cat. No. 128, Nahant, August, 1861, A. Agassiz. Hydrarium. 

 Cat. No. 129, Nahant, September, 1854, H. J. Clark. Hydrarium. 

 Cat. No. 130, Nahant, December, 1854, H. J. Clark. Hydrarium. 

 Cat. No. 131, Nahant, March, 1856, H. J. Clark. Hydrarium. 

 Cat. No. 400, Nahant, Mass., 1862, A. Agassiz. 

 Cat. No. 414, Mingan Islands, N. S., Anticosti Expedition, 1861. 

 Museum Diagram No. 18, after L. Agassiz. 



Family EUOOPID^ Gegenb. 



Eucopidce Geg. (emend Agass.). Zeit. f. Wiss. Zool., p. 241. 1856. 

 EucopidcB Agass. Cont. Nat. Hist. U. S., IV. p. 351. 1862. 



Great confusion has always existed in the identifications made of the 

 different species of Campanularians, on account of the difficulty of dis- 

 tinguishing in certain stages closely allied species. If, however, we 

 are fortunate enough to examine them at the breeding season, when 

 the characteristic reproductive calycles of the different species are in 

 their full development, our task will be greatly facilitated ; and any 

 doubts we may still have of the identity or difference of closely allied 

 species will be entirely removed, should we succeed in tracing the 

 development of the young Medusa. Although we may find it impos- 

 sible to distinguish, at certain stages of growth, young Medusae, it 

 by no means follows that these Medusae, which have developed from 

 Campanularians easily distinguished, are identical. (Compare the dif- 

 ferent Campanularians figured in the sequel.) Whenever we succeed 

 in tracing the complete history of any one of our Jelly-fishes, we 

 always find that we are able to distinguish readily closely allied 

 species, which our previous ignorance had led us to consider as 



NO. II. 11 



