ZANCLEA. 187 



but it seems hardly more serviceable to describe it as a new species without 

 the knowledge of the hydroid than it would be to name a new siphonophore 

 from the medusoid gonophore alone. 



Cladonemidae Haeckel, 1879. 



sens. em. Vanhoffen ('89) ; Hartlaub (: 07). 



Anthomedusae in which the tentacles are either branched, or bear 

 stalked cnidoblasts ; with 4-8 radial canals. 



Zanclea Gegenbaur, 1856. 



Gemmaria McCrady, 1857. 



sens. em. Hartlaub, : 07. 



Cladonemidae with either two or four hollow tentacles, which bear on 

 the aboral side nematocysts mounted on contractile filaments ; four simple 

 radial canals ; manubrium without apical extension ; gonads primarily inter- 

 radial ; no ocelli. 



This definition is that proposed by Hartlaub (: 07). Hargitt (:08), who 

 agrees with him in uniting Gemmaria with the genus Corynites as defined 

 by A. Agassiz ('65) and later authors {non Corynites McCrady), believes 

 that the number of tentacles is a character of sufficient importance to 

 warrant the retention of Gemmaria with two, as distinguished from Zanclea 

 with four; but although he found only two tentacles in the Mediterranean 

 species Z. implexa Alder, Hartlaub (: 07) has recorded four tentacles in 

 occasional very large specimens of this species. However, as Hartlaub 

 (: 07) says, the question is still an open one ; and the present series does not 

 supply the answer. 



The medusae of the various species of Zanclea are so similar one to 

 another that it is difficult to find satisfactory characters by which to 

 separate them; for the certain identification of a given series a knowledge 

 of the hydroid stage is essential. Characters which have been regarded as 

 of taxonomic importance in the medusae are the form of the bell, the form 

 and extent of the exumbral nematocyst ridges, the form of the tentacular 

 nematocyst batteries, the structure of the mouth, whether with or without 

 lips, and the number of tentacles ; but this last character, as pointed out 

 above, may perhaps be of generic significance. 



The present collection contains five specimens, which closely resemble 



