T 



HYDROMEDUSAE FROM THE 

 DISCOVERY COLLECTIONS 



By P. L. Kramp 



Zoological Museum, Copenhagen, Denmark 



(Plates I-VII, text-figs. 1-19) 



INTRODUCTION 



HE Discovery collections of Hydromedusae dealt with in the present paper comprise 85 species, 

 namely, 25 Anthomedusae, 19 Leptomedusae, 4 Limnomedusae, 22 Trachymedusae, and 



15 Narcomedusae. The following species, the type specimens of which are in the British Museum 



(Natural History), are described as new: 



Euphysora gigantea sp.n. Leuckartiara annexa sp.n. 



Ectopleura sacculifera sp.n. Russellia mirabilis g.n., sp.n. 



Rathkea africana sp.n. Amphogona apicata sp.n. 

 Merga rubra sp.n. 



Many species are represented by numerous specimens, but these do not represent the total numbers 

 caught in the nets, but only those picked out from the samples and sent to me for examination. 



Under each species are given the most important references to the literature, a list of stations where 

 the species was collected, its history (where necessary), some remarks on the morphology (except 

 in the case of very well-known species) and the geographical distribution. 



The lists of stations usually comprise all details of date, depth, etc., but in the case of 17 of the most 

 common species these are given in tabular form in Table i . 



The specimens are preserved in formalin, and in comparison with the collections from most other 

 great expeditions the state of preservation is generally very satisfactory, so that it has been possible 

 to make valuable additions to our knowledge of the morphology of several species. Most species of 

 Narcomedusae are, however, extremely fragile, and unfortunately within this group many specimens 

 were indeterminable. However, the collection of Narcomedusae is extensive, and from the material 

 in more or less fair condition and representing several species I have been able to make important 

 progress towards a revision of the species belonging to the genera Pegantha, Solmissus and Cunina, by 

 means of characters to which little attention was paid before. A reliable revision of these medusae, 

 however, requires the study of living specimens. 



Vanhoffen's incomplete descriptions are frequently a severe obstacle to our attempts to identify the 

 species established by him. I have been fortunate enough to unravel his species of the genus Arcta- 

 podema (of the Trachymedusae), three of which are represented in the Discovery collection. Moreover, 

 the extensive material of HaUcreidae has convinced me of the correctness of my previous conception 

 of the delimitation of the species of this family, four of which were established by Vanhoffen. Some 

 critical remarks on the tendency by M. E. Thiel to unite several different species are also given. 



A comparison of Haeckel's original specimens of Boiigainvillia platygaster (which are in the Zoo- 

 logical Museum of Copenhagen) with several specimens in the Discovery collections has enabled me 

 to state the position of this species which has been open to question, and its interesting method of 

 asexual propagation is described here for the first time. 



