416 Dr. Baird on some British Entomostraca. 



Genus 3. Canthocarpus, Westwood MSS. 



Foot-jaws small, simple; second or inferior pair of antennae 

 simple ; ovary single.' 



The Cijc. minutus, Miill., is the type of the genus. 



Genus 4. Arpacticus, M. Edwards. 



Foot-jaws possessing strong hooked claws at their extremity ; 

 second or inferior pair of antennae simple ; external ovary single. 

 The Cyc. cheliferj MiilL, is the type of this genus. 



Genus 5. Alteutha, Baird. 



Foot-jaws small, simple ; body flat ; two strong falciform ap- 

 pendages from fifth segment of body. 



The Cyclops depressus, Baird, is the type and only known spe- 

 cies of this genus. 



Genus Arpacticus. 



Spec. A. nobilis, Baird, Trans. Berw. Nat. Club, 1845. 

 PI. IX. f. 5. 



Thoracic and abdominal portions of body distinct from each 

 other. The thorax is composed of four segments and is large 

 and rounded. Abdomen consists of six slender segments, the 

 last bilobed, and giving off two long and two short setse. The 

 whole insect is beautifully coloured with green, red and purple. 

 Eye large, of a ruby colour. Antennse (f. 5 a) short, of seven 

 segments, all setiferous ; the two first short and stout, the third 

 much longer, toothed on upper edge and giving ofi" at its extre- 

 mity several long setse ; four last small and short. Antennules 

 (f. 5 b) composed of two segments, the first giving off a shoot 

 from about the middle of its length, the second terminating in 

 several stout setse. The mandibles and anterior or first pair of 

 foot-jaws are strong, and resemble the same organs in Cyclops 

 quadricornis. Posterior foot-jaws (f. 5 c) shorter and stouter than 

 those of typical species, and consisting of two joints and a ter- 

 minal hooked claw. Thoracic pair of feet (f. 5 d) differ from ab- 

 dominal ones. They consist of two stalks rising from a common 

 base ; the anterior or upper stalk consisting of one long joint, and 

 a very short one which terminates in a strong claw ; the posterior 

 or inferior stalk is very short, toothed on the edge and giving oiF 

 several stout setse. The abdominal feet resemble those of the 

 typical species, the setse with which they and the fulcra are pro- 

 vided being all plumose. The fulcra are the same also as in the 

 other species. The setse of the tail however are not plumose. 

 This species is at least three times larger than the chelifer, and 

 has the body more rounded and much stouter. 



Hab. Berwick Bay. 



