332 History of British Entomostraca. 



in a short obtuse point ; tail about one-third the length of the body, 

 terminating in two very small lobes, from which issue two very short 

 setae. Eye situated rather lower down than usual in the other spe- 

 cies, of a line ruby colour. Antennae short, strong, subcylindrical, 

 setiferous, of about six articulations ; in the female having a lateral 

 ring at junction of fourth and fifth ; swelling in the male, (Fig. 10) 

 situate in the fourth, followed by the usual hinge-joint, and termi- 

 nating in a hook. Antennules of two articulations, the latter being 

 terminated by about four short setae. From opaqueness of body and 

 flat form, I could not distinctly perceive the mandibles or hands, ex- 

 cept that the latter were terminated by a curved hook as in minutus, 

 fyc. Thoracic pair of feet consist of two stalks as usual, rising from 

 one common base, each stalk consisting of three distinct joints, (Fig. 

 11.) Superior or external stalk longer than inferior one, the last joint 

 terminating in four short hooks. Inferior stalk terminated by seve- 

 ral short setae, and having a long seta given off at each joint. Ab- 

 dominal legs, of the same form and structure as in the other species, 

 and provided with numerous long hairs or setae. Sexual organ of 

 male ? (Fig. 12,) very large, consisting of a broad plate issuing from 

 junction of first with second segment of tail, terminating in a pretty 

 long, bluntish, hollow spine, and having four short teeth or hollow 

 spines on outer edge ; the whole organ being nearly of an equal length 

 with the tail. In the female the fulcra or supports issue from same 

 place, and so nearly resemble the male organ as to make them ap- 

 pear the same. They are not so broad, however, and have only 

 two lateral teeth, both of which are situate near the base. In the 

 female the second segment of tail is much larger than in male. 



The posterior two-thirds of thoracic segment is marked with a 

 broad fascia of a very dark colour, with a ruby tinge in it. Two up- 

 per segments of tail are marked in the same manner, but not of so 

 deep a colour. I have met with but few specimens of this very 

 pretty species, and never with a female with ova. 



The motion of this insect is peculiar. It generally swims on its 

 back, and instead of darting for ward through the water, as the other 

 species of Cyclops do, it springs with a bound from the bottom of the 

 vessel where it rests when undisturbed, up to the surface of the 

 water. For this purpose it curls its body up into the form of a ball, 

 and then suddenly returning to the straight position, springs with a 

 sudden bound from the bottom to the surface, falling gradually down 

 again to the same place from which it sprung. 



I have noticed one or two other marine species of Cyclops on the 



