321 



Bergroth, E., Anmärkningar om fiskfaunen i nedra Irtisch og Ob. Fra Öfvers. 



Finsk. Vet. Soc. Förhdlg. 22. Bd. p. 1 — 8. 

 Day, F., On the fishes of Weston-super-mare. With 2 pi. in: Proc. Zool. 



Soc. London, 1879. P. 4. p. 742—763. 



191 sp.) 



Feddersen, Arth., Fortegnelse over de danske Ferskvandfiske. in: Naturhist. 

 Tidsskr. 12. Bd. 1./2. Hft. p. 69 — 96. 

 (44 sp.) 



Jacoby, L., Der Fischfang in der Lagune von Comaccliio nebst einer Dar- 

 stellung der Aal frage. Mit 2 Taf. Berlin, Hirschwald, 188Ü. 8". (VI, 

 93 p.) ^ 1, 80. 



Tillier, L., Essai sur la distribution géographique des Poissons de mer. (Suite ^ 

 et Fin.) in: Revue Scienc. Natur. Montpellier, N. S. T. I. No. 4. p. 442 

 — 448. 



Wintàer, Geo., Prodromus Ichthyologie Danicae marinae : Fortegnelse over de 

 i de danske Farvande hidtil fundne Fiske. in: Naturhist. Tidsskr. 12. Bd. 

 1./2. Hft. p. 1—68. 



(129 sp.; geographische Übersichten.) 



Bassani, Fr., Vorläufige Mittheilungen über die [fossile] Fischfauna der Insel 

 Lesina. in: Verhandl. k. k. geol. Reichsanst. 1879. No. 8. p. 162 — 170. 



ßetzius , Gst., Das Riechepithel der Cyclostomen. Mit l Taf. in: Arch, für 

 Anat. u. Entwick. 1880. l. Heft, p. 9—23. 



II. Wissenschaftliclie Mittheilimgen. 



1. On a fresh-water Medusa of the order Trachomedusae. 



By E. Ray'Lankester , F. R. S., Professor of Zoology in University 

 College, London. 



On Thursday, June 10th, Mr. So werby, secretary of the Botanical 

 Society of London, observed in the Tank in the water làly house, Re- 

 gents Park, some medusa-like organisms of which he was kind enough 

 to place a large number at my disposal on the following Monday. 



The organism proves to be an adult Medusa belonging to the 

 order Trachomedusae and the family Petasidae of Haeckel's system 

 (System der Medusen, I. Theil). It comes nearest among described 

 genera to Fritz M ü 1 1 e r 's imperfectly known- Aglauropsis from the 

 coast of Brazil. 



The most obviously interesting matter about the form under notice 

 is that it occurs in great abundance in perfectly fresh water at a tem- 

 perature of 90" F . Hitherto no medusa of any order has been detected 

 in fresh water except perhaps some stray estuarine forms. It is ex- 

 ceedingly difficult to trace the introduction of this animal into the tank 



in the Regents Park, since no plants have been recently (within twelve 



24» * 



