HYDRAID^. 



197 



Family HYDRAID^ Gray. 



Hiiitraidce Gray. Syn. Brit. Mus., p. Tfi. 1S40. 

 Hi/drina Eiirenb. (p. p.). Corall. d. Ruth. Jleeres, p. G7. 

 UydraidcB Jousst. Brit. Zooph., p. 120, Second Edition. 



HYDRA Linn. 



Hydra Linn. Syst. Nat. 1 756. 



Hydra gracilis Agass. 



Ilijdra gracilis Agass. ; in Proc. Bost. Soc. Nat. Hist., III. p. 354. 

 Hydra gracilis Ayres ; in Proc. Bost. Soc. Nat. Hist., V. p. 103. 



Our fresh-water Hydra has as yet been studied so insufficiently, 

 that I am unable to add anything respecting the development of the 

 Meduste, or concerning its identity with the European Ili/dra viridi'^. 

 Agassiz has described two Eastern species under the name of Hydra 

 gracilis and II. carnea, and Ayi-es a California species. From the 

 character of the Medusae of the Hydra, it seems to me that it finds 

 its natural place among the true Hydroids, and not among the Dis- 

 cophora?, with which it has usually been associated, on account of its 

 close resemblance to the Scyphistoma [Hydra tuba). 



Cambridge (L. Agassiz). 



Cat. No. 370, Cambridge, 18G2, W. Glen. 



Hydra carnea Agass. 



Hydra carnea Agass. ; in Proc. Bost. Soc. Nat. Hist., HI. p. 354. 



Hydra carnea Ayues ; in Proc. Bost. Soc. Nat. Hist., V. p. 104. 



Massachusetts and Connecticut (Agassiz ; Ayres). 



Hydra tenuis Avrf.s. 



Hydra tenuis Ayres ; in Proc. Bost. Soc. Nat. Hist., V. p. 104. 



San Francisco, California (Ayres). 



