170 



the longer. Last pair of legs exhibiting a rudimentary condition similar to 

 those in the preceding species, the spine being however less slender, almost 

 knife-shaped, and pointing backwards. Ovisacs of moderate size, oblong oval 

 in form, and closely applied to the sides of the tail. 



Male much smaller than female, and exhibiting the usual sexual 

 differences. Dactylus of the posterior maxillipeds very slender and abruptly 

 curved in the middle, terminating in a small knob-like dilatation. 



Body in both sexes of a whitish grey colour, with a more or less 

 distinct violaceous tinge. 



Length of adult female amounting to 1.30 mm., of male to 0.90 mm. 



Remarks. This form was announced as early as the year 1875 by 

 Brady and Robertson, and was subsequently more fully described and figured 

 by the former author in this well-known Monograph as a species of the genus 

 Lichomolgus. Canu was the first to recognise the true systematic position of 

 this form within the genus Pseiidanthessius of Glaus. From the type of this 

 genus, P. gracilis, it is at once distinguished by the short, compact shape 

 of the body, in which respect it exhibits a perplexing similarity to an other- 

 wise "very different form, viz., Echinocheres violaceus belonging to the sipho- 

 nostomous Cyclopoida (compare the figure here given with that of the latter 

 form on PI. LVIII). 



Occurrence.- I have met with the present form in several places, both 

 on the west and south coasts of Norway, as also in the upper part of the Chri- 

 stiania Fjord. It is not unfrequently found in the free condition among dredged 

 material, and this indeed induced Brady to give it the rather inappropriate 

 specific name liber. I have however, in several instances been enabled to 

 ascertain its parasitic nature, having found it not unfrequently in considerable 

 numbers clinging to the surface of various Echinids, for instance Echinus 

 sphcera and Strongylocentrotus drobakiensis. 



Distribution. British Isles (Brady), Ceylon (A. Scott). 



91. Pseudanthessius assimilis, G. O. Sars, n. sp. 



(PI. XCV). 



Specific Characters. Female. Very like the preceding species, but of 

 much larger size, and having the anterior division broader in front than behind. 

 Tail considerably exceeding half the length of the anterior division; genital 

 segment comparatively large, and of a similar form to that in P. liber; anal 

 segment, however, much (nearly twice) larger than the preceding segment 



