6 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



characteristics of the Charybdeidaa and two of the Chirodropidae. The 

 family was named from the prominent feature of the arrangement of 

 the tentacles, in groups of three with separate pedalia. The small size 

 of T. cystophora is worthy of note in connection with the fact that of the 

 twenty species of Cubomedusas given by Haeckel in his " System " only 

 two are smaller than 20 mm. in height, and those are the two representa- 

 tives of Haeckel's genus Procharagma, the prototype form of the Cubo- 

 medusaB, without pedalia and without velarium. While Tripedalia has 

 both pedalia and velarium, it may be perhaps that its small size, taken 

 in connection with characteristics just about midway between the 

 Charybdeidas and the Chirodropidas, indicate that it is not a recently 

 acquired form of the Cubomedusas. 



