366 HYDROID^. Part IV. 



Rhopalonema Gegenb. — Calyptra XeMC/(". (preoccupied among Mollusca). 

 R. velatum Geyenh., PI. 9, figs. 1-5. — Calyptra umbilicata Lenclc, 

 PI. 1, figs. 9 and 10. — Nice (Leuckart) ; 3Iessina (Gegenbaur). 

 Hypsonema ^_(/. — Cytceis Will. 



H. polystyla Ag. — CytEeis polystyla Will, PI. 2, fig. 5. — Adriatic : 

 Trieste (Will). 

 Gossea Ag. — Thaumantias Gosse (p. p.). 



G. Corynetes Ag. — Thaumantias Corynetes Gosse, Devon., PI. 21 ; 

 fig. 1, PI. 22, may be the young. — Devonshire Coast (Gosse). 

 5th Sub-order. PORPIT^E Gohlf? — Chondrophorae Cham, and Eysenh. 



1st Family. Velellid.e Esch. (restricted). This fiimily is readily distin- 

 guished by its oblong form and crested disk. 

 Velella Lmlt. — Holothuria ForsJc. — Phyllodoce Br. — Armenistarium 

 Costa. — Rataria Esch. (young). — The free Medusas : Chryso- 

 mitra Gcgenh., and Linuche Esch. — For the development of 

 the Hydra, see Huxley, p. 114, and PI. 11. 

 V. spirans Esch. — Holothuria spirans ForsJc; Kdll, PI. 11; Vogt, 



PI. 1 & 2; Lcuch, PL 13, fig. 11. — Mediterranean (Forskal). 

 V. mutica Bosc ; Ag., pp. 83 and 110. — Gulf of Mexico (Brown, 

 Bosc) ; Coast of Florida (Agassiz). 

 2d Family. Porpitid.e Guild. — Velellidse Esch., (p. p.). — Form circular, no 

 crest. 

 Porpita Lmk. — Holothuria ForsJc. — Polybrachionia L. Guild. — Ratis 

 Less. — Acies Less. 

 P. mediterranea EscJi.; Kdll, PI. 12. — Holothuria denudata ForsJc. — 



Mediterranean (Forskal). 

 P. linnseana Less. — Polybrachionia linnaeaua L. Guild. — Antilles 

 (Guilding); Florida (Agassiz); Charleston (McCrady). 

 Gth Sub-order. PHYSALI^E Less. — Thus far only one family, Physalid^ Br., 

 with a single genus : 

 P h y s al i a LmJc. — Holothuria L. — Salacia L. — Arethusa Br. — Thalia 

 Brug. — Cystisoma Less. — Young Hydra in Huxl, PI. 10. 



^ In characterizing this and the following sub- in our science, that special names are required to 



orders, p. 334, I have purposely avoided the special designate the parts of animals, the homologies of 



nomenclature, devised by the German naturalists which are not fully ascertained ; but as soon as their 



to describe the Siphonophora% and reproduced in structural identity ceases to be doubtful, it seems to 



an hellenic garb by Huxley, in order the more me best to discard such technicalities, and I believe 



directly to show the close affinity of these animals the time has come when the Siphonophoraj may 



with the Hydroids. It is a fact constantly recurring be described in the same words as other Acalephs. 



