VALVIFERA ASELLOTA 



I 2 



of the mouth-parts, while the maxillipedes undergo an enlarge- 

 ment, and are used for causing a current through the brood- 

 chamber. 



Sub-Order 3. Valvifera. 



The Valvifera, illustrated by the Idotheidae and Arcturidae, 

 are characterised by the uropods being turned back and expanded 

 to form folding doors covering up the delicate pleopods, which are 

 mostly respiratory 

 in function, though 

 the anterior pairs 

 may serve as swim- 

 ming organs. Arc- 

 turus is a typically 

 deep sea genus, 

 many species, re- 

 markably furnished 

 with spiny processes, 

 having been taken 

 by the Challenger in 

 the southern hemi- 

 sphere. The Ido- 

 theidae are more lit- 

 toral forms, several 



of III at In, i 



commonly 



met with off the v )fi^/ 



British coasts, oc- 

 casionally penetrat- 

 ing into brackish or 

 even fresh water. 



being 



FK;. 8-5. 



(Munnopsidae), c5 , > 



I/-. :il>ilciiiii-n : '/'. .Mil thoracic appendagi 

 or 4tli leg. (Alter Sars.) 



Sub-Order 4 

 Asellota. 



In Ui is 



the abdominal segments are 1'used dorsally Id lurm a shield-like 

 caudal region; the pleopods are respiratory in I'uiiet ion and 

 reduced in numbers, the first pair being often expanded and 

 produced backwards to form an operculum covering the i 

 Several of the Asellota are fresh-water. J.sv//Vs <i<j,i,ifi<'t'x 



