ME, E. J. MIEES ON THE IDOTEIDiE. 7 



Body ovate, with tlie ejiimera not distinctly separated by a 

 sutui'e from the thoracic segments. Postabdomen nearly always 

 uniarticulate. Antennse with the flagellum rudimentary, few- 

 jointed, or mnltiarticulated. Basal opercular plates with an 

 oblique line crossing their outer surface. Edotia. 



Body slender and more or less oblong-ovate, with the epimera 

 small but distinct, and some or all evident in a dorsal view. 

 Postabdomen composed of one to five distinct segments. An- 

 tennse with the. joints of the flagellum consolidated into a single 

 piece. Cleantis. 



These four genera appear to me to indicate the natural groups 

 into which the family may be subdivided ; but it must be noted 

 that (as in all classifications) species in some degree intermediate 

 occur. Thus in Idotea 2)i^ismatica the flagellar segments of the 

 antenufe are occasionally partially consolidated, and this species 

 in many other of its characters approaches very nearly to 

 Oleantis; and in Idotea Jiectica the epimera are not distinct, yet in 

 its three-jointed postabdomen and in all other characters this 

 species belongs to Idotea rather than to I^dotia. 



The principal characters for distinguishing the species of this 

 group are to be found in the form and the degree of convexity 

 and tuberculation of the segments of the body, the relative length 

 of the antennse and of their constituent joints, and similar struc- 

 tural details ; the coloration, although occasionally characteristic, 

 is not apparently generally to be relied upon as of great im- 

 portance in the classification f. 



List of the G-eneea and Species. 



IDOTEIDiE. 



Subfam. Glyptonotin^. 

 Glyptonotus. 



*1. G. antarcticus, Eights. New South Shetlands. 



2. G. entomon (Linn.). Baltic and circumpolar seas. 



3. G. Sabini (Kroyer). Boreal and circumpolar seas. 



4. G. ccscus (Say). East coast of U. States; Nova Scotia. 



*5. G. Tuftsii (Stimpson). East coast of U. States ; Nova Scotia. 



t For some very interestiaig remarks on the influence of tlie light in effecting 

 change of colour in the IdoteidcB (confirmatory of previous observations by 

 Pouchet and Jourdain on other Crustacea), see Dr. Paul Mayer, in Mittheil. 

 Zool. Stat. Naples, i. p. 521 (1879). 



