60 



it very difficult to accept Mœrisia as simply a Margelid devoid of oral 

 tentacles or nematocyst-knobs. 



It must be noted however that Turritopsis pacifica Maas has been 

 described as possessing abaxial ocelli". 



The structure of the hydroid stage of Mœrisia ///oasi suggests that 

 the medusa may have some connection with the Tiaridae; the genus is 

 however very unlike the more typical members of this family, although 

 in some respects resembling certain aberrant genera which A. G. Mayer 

 has grouped together in the tribe Protiaridi 8 . 



The main points of resemblance are the simple mouth, the smooth 

 gonads and the position of the ocelli on the abaxial sides of the tentacle- 

 bulbs. The systematic position of Protiara and its allies is however 

 very uncertain, so that the resemblance to these genera does not help 

 us much in finding a home for Mœrisia. 



The Tiaridae and Margelidae have almost certainly arisen from 

 some simpler forms of Anthomedusae such as those grouped together 

 as the Codonidae, and, taking various considerations into account I 

 think it best to consider Mœrisia as being intermediate between the last 

 two families, its exact systematic position must remain uncertain for 

 the present. 



The occurrence of a species of Mœrisia in the Caspian Sea is of 

 considerable interest. We know that this gigantic lake was once joined 

 to the Black Sea and the faunas of these two pieces of water resemble 

 one another in certain respects, the Caspian basin, moreover, had a 

 communication with the open ocean at some not very remote period. 



When describing the medusa from Lake Qurun 9 1 suggested that 

 this piece of water represents the remains of the sea which covered 

 this part of Northern Africa during Tertiary times and retreated north- 

 wards after this period. The occurrence of species of Mœrisia in these 

 two somewhat remote localities may therefore be explained by consi- 

 dering them as relicts, left behind by the same sea and both gradually 

 accustomed to live in water of considerably less salinity than that of 

 their original home. 



15 ir mi ngham, May 7, 1912. 



C. Hartlaub, 1. c. p. 210. 

 8 A. (i. Mayer. 1. c. ]>. 103. 

 <\ L. Bon le ncrer, 1. c. p. 372. 



