352 



HYDROID.E. 



Part IV. 



E. diaphana Ag., p. 322, PI. 34, figs. 1-9. — Thaumantias diaphana 

 A(/., Mem. Amer. Acad., IV. p. 300, figs. 1 and 2. — Nahant 

 (Agas,siz); Namhon (A. Agassiz). 

 Laomedea Lumx? — Campanularia Lmk. (p. p.). 



L. amphora Ag., p. 311, PI. 30. — Massachusetts Bay (Agassiz). 

 7th Family. Oceanid^ Esch? (So restricted as to exclude the Nucleiferae 

 Less., and the Gerjonopsida^ Ag.). — Eucopidas Gegenb. (p. p.). 

 Oceania Per. and LeS. (restricted). — Thaumantias Esch. — Callichroma 

 Dnjard. — Epenthe.sis 3IcC): — Phialidium Leiick. 



0. phosphorica Per. and LcS. — Thaumantias cymbaloides Esch. — 

 T. hemisphajrica Esch., Forbes, Nak. Med., PI. 8, fig. 2.— English 

 Channel (Peron and LeSueur). — Thaumantias insconspicua 

 Forbes, PI. 8, fig. 3, Hebrides, — T. punctata Forbes, PI. 10, fig. 

 1, Isle of Man, — T. lineata Forbes, PI. 11, fig. 1, Zetland,— 

 T. pileata Forbes, PI. 11, fig. 2, North Ireland, — T. sarnica 

 Forbes, PI. 11, fig. 4, Guernsey, — are probably different stages 

 of growth only of T. hemisphairica. — Oceania ampullacea Bars, 

 belongs also to this series. 



* Without a renewed comparison, it is impos- 

 sible for me to refer to tlieir proper genus, tlie 

 many species of Campanularia and Laomedea al- 

 ready described, since it is known that among them 

 there are types of different genera ; belonging even 

 to different families. 



- Compare note 2, p. 346. It is far more diffi- 

 cult to define correctly the families of this sub-order, 

 than those of the Tubularians, for the simple reason 

 that comparatively few free Mcdusic of this type 

 can be referred with certainty to the Ilydroids 

 from wliich they arise, and the mcdusavbuds of a 

 larce number of the Ilvdroids, have not been 

 observed at all. Under these circumstances, the 

 attempt at a classification, here presented, should 

 be considered as containing hints, rather than ma- 

 ture results. Starting, however, from jirinciples 

 which have proved a safe guide, whenever the 

 data on hand were sufficient, I have considered 

 as belonging to distinct families all those free 

 Medustie and Hydroids which have distinct patterns. 

 Thus, the Aglauridse are separated on account of 

 the flat-topped bell, and the position of their re- 



productive organs, even though their mode of 

 reproduction is unknown. To the characters as- 

 signed to the Circei(hK by Forbes, I would add 

 their elongated, cylindrical form. The PolyorchidiB 

 are quite remarkable for their branching, chymifer- 

 ous tubes, and their pendent, reproductive organs ; 

 the Melicertidic for their eight radiating tubes, 

 their lobed, reproductive organs, and their wide 

 and short actinostorae ; the Laodiceidaj for their 

 flat form, the extensive lobes of their actinostome, 

 and their peculiar marginal appendages. The free 

 medusa of Lafoca cornuta Lamx., lately observed, 

 and the peculiarities of this Ilydroid, show that 

 this family cannot be united with the Oceanida^ 

 proper, and still less with the Geryonida^ with 

 which Forbes associates them. Gegenbauer has 

 appreciated their difference correctly ; but he has 

 given them a name which cannot be retained. 

 All these families are destitute of eyes, and have 

 only an accumulation of pigment upon the base 

 of the tentacles, or cirrhi alternating with them. 

 The Eucopidaj and Oceanida^, on the contrary, have 

 distinct eyes ; but in tiie Eucopidai they are at- 



