ME. E, J. MIERS ON THE IDOTEID^. 5 



minate in a subprehensile hand formed by the flexion of the ter- 

 minal joint or dactylus upon the more or less dihited penultimate 

 joint or propus. The first five pairs of postahdomiual appendages 

 are delicate and membranaceous, and are covered by the oper- 

 culum, vphich is specially characteristic of this family. The oper- 

 culum is composed of the greatly elongated and dilated bases and 

 the interior rami of the posterior pair of postabdominal appendages 

 or uropoda, which constitute a pair of longitudinally folding doors, 

 closing over the ventral surface of the postabdomen ; the exterior 

 rami are also occasionally present as small lamellae articulating 

 with the basal plates of the operculum. 



The IdoteiclcB are found in all parts of the globe, but appear to 

 be more abundant in the temperate and colder seas than in the 

 tropics. They occur usually at moderate depths along the coast 

 and often amid the seaweed, on either sandy, muddy, or rocky 

 bottoms. Some species also may occur at considerable depths : 

 thus Glyptonotus entomon has been taken at a depth of 60 fathoms 

 in the Baltic (Mobius), and Edotia nochilosa at 190 fathoms oif 

 Halifax (Harger). Idotea tnetallica is a pelagic species found 

 upon the surface of the ocean, or amid floating seaweed at great 

 distances from the land, and other species are occasionally found 

 under similar conditions. Although generally marine, certain 

 species inhabit freshwater lakes : instances are the O. entomon, 

 which occurs in the deep Scandinavian lakes AVener and "VYettern 

 (Prof Loven), and Idotea lacustris, which has been found in a fresh- 

 water lagoon in New Zealand by Mr. Thomson, and with which I 

 identify, though with great hesitation, specimens, probably marine, 

 from Port Henr}^, Magellan Strait, in the Museum collection. 



The nearest affinities of the IdoteidcB are with the Arcturidce 

 and with the Chcstiliidce of Prof. Dana — a group founded for the 

 reception of the single genus and species Chcetilia ovata. As no 

 description is given of the buccal organs and of the five anterior 

 pairs of legs in Chcetilia, it is impossible for me to express ix,nj 

 opinion as to whether it should really be retained in a distinct 

 family from the Idoteidce. The multiartieulate character of the 

 sixth and seventh pairs of thoracic legs is probably not a cha- 

 racter of the importance assigned to it by Dana. 



In its ovate form, four-segmented postabdomen, and elongated 

 antennules the relationship of Chief ilia to Glyptototus is obvious ; 

 but the antennules in Chcutilia are placed immediately above the 

 antennae, as in JEdotia, 



