215 



formation) almost perfectly symmetrical, vermiform. Adult male with the segments 

 of metasome more or less fused together. Parasitic on the ventral face of differ- 

 ent Carida. 



Remarks. — This genus was etablished in the year 1843 by H. Rathke, 

 to include a peculiar Bopyrid found by him on a species of Spirontocaris (Hip- 

 polyte), and named Phryxus hippolytes. He, moreover, refers to this genus an- 

 other Bopyrid, P. Paguri, which, however, is now recognized as generically differ- 

 ent and referable to the genus Athelges of Hesse. MM. Giard and Bonnier 

 transfer the generic name Phryxus, proposed by Rathke, to a generically differ- 

 ent exotic Bopyrid, substituting for the northern form a new name, viz. 

 Hemiarthrus. This, however, cannot, be sanctioned, since such a proceed- 

 ing is quite contrary to the general rule in Zoology. If the name Phryxus is 

 to be retained in the present group, it ought certainly to be used for the form, 

 to which it was originally assigned, and cannot be replaced by a new generic 

 name, unless the former name is altogether to be abandoned. It may be that 

 this will be found necessary, as the name Phryxus is said to be already appro- 

 priated in Zoology. 



The present genus exhibits, it is true, some points of agreement with 

 the genus Athelges, especially as regards the structure of the metasome, but in 

 several other respects it differs rather markedly, so that it ought evidently to be 

 kept apart, though forming with it a distinct sub-division of the family Bopyridae. 

 In addition to the northern species described below, MM. Giard and Bonnier 

 have recorded 4 other species from the Mediterranean; but no description or 

 figures of these have as yet been given, and their validity is accordingly still 

 rather problematic. 



Phryxus abdominalis, (Kroyer). 



(PI. xc, SCI). 

 Bopyrus abdominalis, Kroyer, Nat. Tidsskr, Vol. HI, p. 102, PI. I, II. 

 Syn.: Phryxus hippolytes, Rathke 



„ Hemiarthrus abdominalis, Giard and Bonnier. 



Specific Characters. — Body of fully grown female forming an irregular, 

 globular mass, somewhat varying in form, according to the degree of distention 

 of the marsupial pouch, one of the sides, sometimes the left, sometimes the right, 

 being much more swollen than the other, and the axis of the body accordingly 

 more or less twisted to one side or the other. Cephalon comparatively small, 



