370 



Itemarl;.^. — Tlie present genus was established by Owen as early as 

 in the year 1835, but as the name lie propose, Acanthosoma, was already 

 appropriated in Entomology, Boeck changed it, in 1870, to Acanthosone. The 

 genus is chiefl}- characterised by the extraordinaril}' rich spinous armature 

 of the body, to which character may be added several other peculiarities in 

 the structural details, mentioned in the above diagnosis. The genus Arcoi- 

 thecMmts of Stebbing is apparently nearly allied to the present genus, and 

 undoubtedby belongs to the same family, and not, as opined by that author, to 

 the Iphimedidse. The only as j-et known species belonging to the present 

 genus, is the arctic form described in the seqiiel. 



5. Acanthozone cuspidata, (Lepechin). 



>,P\. 130). 

 Oniscus cusjndntus, Lepechin, Acta Petiopol. 247, PI. VIII, fig. 3. 

 Syn : Acanthosoma hystrix, Owen. 

 „ Amphithoe hystrix, KrOyer. 

 ,, Paramphithoi? hystrix, Bnizel. 

 Body not very tumid, nearly cylindric in form. Mesosome with 5 

 longitudinal rows of spines, one dorsal, 2 subdorsal, and 2 lateral; dorsal 

 spines very large, lanceolate, erect, and continued along the metasome, each 

 pointing successively more backwaixls, 1st segment of mesosome with an addi- 

 tional, very large, laminar, dorsal projection turned straight forwards above the 

 cephalon; spines of the siibdorsal keels miich smaller, though somewhat 

 increasing in size backwards, and continued on the first 2 segments of meta- 

 some, 1st segment of mesosome with an additional rather minute subdorsal 

 spine on each side at the base of the anterior dorsal projection; spines of the 

 lateral keels formed bj- the greatl}^ projecting inferior edges of the segments 

 of mesosome. Epimeral plates of metasome divided in the 2 anterior segments 

 into 3, in the last segment into 2 greatly produced spini form lappets, minutely 

 denticulated on the edges. First segment of urosome with a triangular com- 

 pressed dorsal projection, and having besides, like the succeeding segment, 

 just above the insertion of the uropoda, a small, recurved, lateral spine. 

 Cephalon greatly vaulted above, the front being nearly perpendicularly deflexed, 

 rostral projection verj^ small, and horizontally projected, lateral corners 

 forming a very slight, lobular expansion subtruncated al the tip, postantennal 

 ones prolonged to a large anteriorly curving spiniform process. First pair 

 of coxal plates having the anterior corner produced to an acute projection; 

 the 2 succeeding pairs likewise tapering to an acute point, which however 

 turns more downwards; 4th pair somewhat larger than the preceding pairs, 

 and divided at the tip into 2 strong, inferiorly-pointing. spiniform lappets; 

 5tli pair having likewise 2 acute projections, which however turn straight 



