65 



longed and carrying at the outer distal corner the usual slender bristle, distal 

 joint short, lamelliform, constricted at the base and trilobate at the end, carrying 

 2 unequal spines and an intermediate slender seta attached to a conical 

 prominence of the joint. Seminal receptacle with the posterior part more or less 

 distinctly bipartite. 



Remarks. This genus answers to the "fuscus-albidus group" of Dr. Schmeil, 

 and comprises a limited number of species, which are all distinguished by their 

 robust body, the tumid and boldly vaulted anterior division, and the very slender and 

 elongated anterior antenna?. Of anatomical details may be particularly mentioned 

 the characteristic structure of the last pair of legs, which is very unlike that in 

 any of the other known groups of Cyclopses. 3 species belonging to this genus 

 will be described below, and I am inclined to believe, that also the North-American 

 species, Cyclops ater Herrick, may be referable to this genus, though the last 

 pair of legs are said to be uniarticulate. 



38. Pachycyclops signatus (Koch). 



(PI. XL). 



Cyclops signatus, Koch, 1. c. Heft 21, Tab. 8. 

 Syn: Cyclops qvadricornis fuscus, Jurine. 

 coronatus, Claus. 



fuscus, Schmeil. 



Specific Characters. Female: Anterior division of body broadly ovate in 

 outline, greatest width about equalling half the length and occurring in front of 

 the middle. Cephalic segment large and tumid, with the frontal edge narrowly 

 truncated. Last trunk-segment very small and sharply defined from the preceding 

 one. Tail comparatively short, scarcely attaining half the length of the anterior 

 division ; genital segment about the length of the 3 succeeding segments combined, 

 and almost cylindrical in form. Caudal rami rather short, though somewhat 

 longer than the anal segment, and slightly divergent, inner edge finely ciliated; 

 seta of outer edge very small and attached close to the end; apical setae densely 

 plumose and rather spreading, the inner mediate one exceeding the tail in length; 

 seta of outer corner rather elongate, though shorter than that of the inner corner. 

 Anterior antennae very slender and attenuated, reaching, when refiexed, to the 

 end of the 3rd segment, distal edge of the 8th, 9th, llth, 12th and 13th joints 

 distinctly denticulated, the 3 outermost joints very narrow and exhibiting along 

 the upper face a delicate hyaline rib, which on the proximal part of the last 

 joint is divided into 8 strong serrations. Posterior antenna; unusually slender, 

 with the penultimate joint long and narrow, attaining fully the length of the 



9 Crustacea. 



