57 



Remarks. This form, the smallest of all our Cyclopses, has been con- 

 mnded by several authors (Rehberg, Daday, Lande, Richard) with C. diaphanus 

 i^scher, from which it differs in many essential, points, being much more nearly 

 .'latod to C. varleans. From this latter species it may be easily recognised by 

 ts much smaller size, the shorter and only 11-articulate anterior antenna}, and 

 different structure of the caudal setae, finally by the peculiar colouring of the 

 >dy when alive. 



Occurrence. I have only found this form quite occasionally in small 

 glassy ponds near Christiania. In spite of its small size, it may be readily 

 letected, owing to its peculiar and beautiful colour, which character indeed has 

 jiven rise to the specific name proposed. 



Distribution. Sweden (Lilljeborg), Germany (Schmeil), Hungary (Daday), 

 *oland (Lande), France (Richard). 



Gen. 13. MeSOCyClOpS, G. 0. Sars, n. 



Generic Characters. Body more or less slender, with the anterior division 

 generally rather tumid, the posterior very slender. Epimeral parts of the trunk- 

 segments scarcely prominent laterally and, as a rule, not visible in the dorsal 

 aspect of the animal. Last trunk- segment very small, not produced laterally. 

 Genital segment in female rather elongated and very little dilated in front. Caudal 

 rami of moderate length or very short, with all the apical setae generally well deve- 

 loped. Anterior antennae slender and elongated, generally 1 7-articulate. Posterior 

 antenna? likewise slender, with the apical seta? long and curved. Maxillipeds 

 rather fully developed. Natatory legs, as a rule, with both rami 3-articulate; 

 terminal joint of outer ramus in all pairs with only 2 spines outside, its inner 

 edge carrying in the 1st pair 2, in the other pairs 3 setae; terminal joint of inner 

 ramus unusually prolonged, especially in the posterior pairs. Last pair of legs 

 very small and generally biarticulate, distal joint carrying 2 slender subequal setae. 

 Seminal receptacle in all the species of a very characteristic form, anterior part 

 short, bilobular, posterior greatly prolonged, tongue-shaped. 



Remarks. This new genus answers to the group of Cyclopses distinguished 

 by Dr. Schmeil as the "Leuekarti group". The species included in this group 

 differ conspicuously in their external appearance from the more typical Cyclopses 

 described in the preceding pages, and more resemble those belonging to the next 

 genus, Pachy cyclops, with which they also agree in the unusually slender form of 



8 Crustacea. 



