41 



cylindrical in shape, and in most cases only composed of 4 distinctly defined 

 segments. Caudal rami with the setae much obliterated, in some cases apparently 

 wholly absent, in other cases replaced by curved hooks. Anterior antennae 

 short and stout, deflexed, with the number of joints more or less reduced; 

 those in male, as a rule, of the very same structure as in female. Posterior 

 antennae distinctly prehensile, terminating in a more or less strong claw. Oral 

 parts on the whole well developed, though the posterior maxillipeds in some 

 cases may be rather reduced. The 4 anterior pairs of legs, as a rule, not 

 adapted for swimming, and of somewhat different structure in the different 

 genera. Last pair of legs generally less rudimentary than in the Notodelphyidce, 

 rarely quite absent. 



Remarks. This family was proposed in the year 1878 by Prof. Brady, 

 to include (he 3 genera Doropygus, Notopterophonis and Botachus, which 

 formerly were referred by Thorell to his family Notodelphyidce. I am of 

 opinion that this family ought to be maintained, although indeed some of the 

 forms apparently exhibit a rather close relationship to the genus Notodelphys. 

 However, as indicated in the above-given general characteristic of the family, 

 certain very conspicuous peculiarities are found, which are common to all the 

 forms, and by which the present family seems in reality to distinguish itself 

 pretty well. Several well marked types are comprised within the family, and 

 this has rendered it necessary to establish rather a great number of genera, 

 some of which have been formerly combined within the genus Doropygus of 

 Thorell. Seven different genera belonging to the present family will be treated 

 of in the sequel, and 3 other genera, not represented in the Fauna of Norway, 

 are also evidently referable to the same family, viz., Goniodelphys Buchholtz, 

 Doroixys Kerschner, and Bonnlerilla Canu. The family thus comprises at 

 present no less than 10 genera. 



As to habits, the forms comprised within this family agree with the 

 Notodelphyidce in so far that they, like the latter, lead a symbiotic existence 

 within the branchial cavity of several kinds of Ascidians. Their mobility is 

 however far inferior, and they seem indeed in most cases to be wholly devoid 

 of swimming power, being only enabled to change their place within the 

 branchial cavity of their hosts by a slow ramping motion. This applies not 

 only to the females, but also to the males, with perhaps a single exception, 

 viz., Doropygopsis longicauda (see farther below). ' 



6 Crustacea. 



