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joint, at some distance from the end, of moderate length. Posterior antennas 

 with the outer ramus very small and provided with only a single minute 

 bristle; terminal joint longer than the penultimate one and somewhat curved in 

 its outer part, seta of outer edge attached at a short distance from the end. 

 Siphon extending only slightly beyond the insertion of the posterior maxillipeds. 

 Maxillae with the outer lobe scarcely half as long as the inner; apical setae of 

 both lobes rather slender. Anterior maxillipeds with the dactylus exceedingly 

 strong and hamiformly curved at the end; secondary spine small. Posterior 

 maxillipeds more normally developed, terminal claw of the dactylus occupying 

 about half its length, and finely denticulate inside. 1st pair of natatory legs 

 somewhat smaller than the 2 succeeding ones, and having the terminal joint of 

 outer ramus of moderate size and provided outside with 3 spines and inside 

 with 3 seta?. Inner ramus of 3rd pair differing from that of 2nd pair in the 

 absence of the usual apical spine. Not even the slightest rudiment of a 4th pair 

 present. Last pair of legs only represented by 3 small bristles, all issuing 

 immediately from the sides of the corresponding segment. Lateral ca>ca of 

 intestine very fully developed, extending along the sides of the cephalic segment 

 and also penetrating into the adjacent part of the trunk, being divided outside 

 into numerous narrow lobules. Ovisacs globular in form and wholly concealed 

 beneath the posterior part of the trunk. 



Body of a light yellowish brown colour, with the intestine and its lateral 

 co?ca of a darker hue; ova in the ovisacs orange-coloured. 



Length of adult female about 2 mm. 



Male (at least in its adult state) unknown. 1 ) 



Remarks. The present Copepod cannot be confounded with any of the 

 other siphonostomous Cyclopoida, being clearly distinguished by the pronouncedly 

 clypeiform shape of the body and its nearly circular form. It is however not 

 improbable that the hitherto unknown female of Dystrogus will be found to 

 approach nearer to Artotro</tt in the general form of the body than does the male. 



Occurrence. This peculiar form was observed by my late father at 

 a very early period, at Manger, north of Bergen, where several specimens were 

 taken by him from nudibranchiate Mollusca. The specimen described by Boeck 

 was found by him on a species of Doris taken at Farsund, south coast of Norway. 

 I have myself met with this form in two widely distant localities of the Norwegian 

 coast, viz., at Kleven, near Mandal, and at Hasvig, western Finmark. In both 



l ) It is very questionable if the specimen described by Scott as the male of the present 

 form was in reality of that sex. and T think that Uiesbreclit was rig-lit in believing; it to be 

 quite an immature form, in -which the sexual characters had not yet appeared. 



