MK. E. J. MTEES ON THE IDOTEID^. 25 



a. Terminal segment dentated or subtruncated or rounded at Us 



distal end. 

 As the form of the epimera is not known in all of the species 

 of this subsection, I hare not been able to make use of this 

 character in the following analysis of the species to as large an 

 extent as its importance deserves. 



* Terminal segment distinctly toothed or acute at its distal end. 



Oblong-ovate : terminal segment tricuspidate, or more or less 

 acute at its distal end. 1. /. marina (Linn.). 



Oblong-ovate": terminal segment with a blunt median tooth 

 at its distal end. 2. I. Whitei, Stimpson. 



Oblong, with subparallel sides : terminal segment more or less 

 triangulate. 3. /. ochotensis, Brandt. 



Slender-linear : terminal segment with the prominent postero- 

 lateral angles separated by a tooth from the blunt median portion. 



4. /. iirotoma, Stimpson. 



** Terminal segment subtruncated at its distal end. 

 a. Body oblong-ovate. 

 Front entire : epimera with the postero-lateral angles more 

 or less projecting ; terminal segment not carinated. 



5. /. metallica, Bosc. 

 Front apiculate in the middle : terminal segment not carinated. 



6. /. margaritacea, Dana. 

 Terminal segment carinated above ; joints of the peduncle of 



the antennae elongated. 7. /. pusttdata, Eisso. 



/3. Body slender, filiform. 



8. /. ? qracillima, Dana. 



*** Terminal segment regularly rounded at its distal end. 

 "With a small median point: epimera of second and third 

 segments not quite reaching to postero-lateral angles of these 

 segments. 9. I. WosnesensTcii, Brandt. 



Entire : epimera reaching quite to postero-lateral angles. 



10. /. lacustris, Thomson ? 

 Idotea maeina. 



Oniscus marinus, Linn. Fauna Suecica, p. 500 (1761) ; &'yst. Nat. (ed. 



xii.) p. 1060 (1766); Pennant, Brit. Zool. iv. p. 38, pi. xviii. fig. 3 



(1777) ; Fabr. Mantissa Ins. i. p. 241 (1787). 

 Oniscus tridensj Scopoli, Entom. Carniolica, p. 415 (1763) ; Olivier, 



Ency cl Meth. vi. p. 26 (1791). 



