39 



The only exclusive character I have been able to find 

 for bringing proofs for the division of the genus Armadillo 

 is owing to studies with the mouth-parts, these shall be 

 described below, and these terms will also be certainl}^ es- 

 sential. Among the other characters to which I shall call 

 attention are principall}^ two, which until now have been 

 disregarded. The dorsal plates of the segments are divided 

 in a foremost and a hindermost part, separated by a su- 

 ture. The foremost part, I call pronotum. During the 

 conglobation the pronotum and a greater or smaller portion 

 of the hindermost part slides under the underside of the 

 proceeding segment, and the size of the pronotum is very 

 different; usually it is larger, when the isopod is less able 

 to conglobation. One shall find application for this charac- 

 ter under a great many circumstances, unfortunately a care- 

 full examination demands the dissection of the specimen. 

 Not only the form of the connexion between the individual 

 segments of the body, but also between the first segment 

 of the truncus and the head, a connexion usually very firm, 

 has fixed marks as well in the articular surfaces as in the 

 position of the eyes and of the antennae, and these marks 

 are of importance. Also here is unfortunately a decapitatio 

 necessary. 



The second character I have chiefly used for classifica- 

 tion is the appearance of the trachese in the exterior branch 

 of the pleopodes. With reference to this character the 

 female alone is taken in consideration, the reason for which 

 will be shown in the following remarks. The exterior 

 branch of the pleopodes in all Isopod s appears, as is well 

 known, as a deckplate for the innerbranch, which is deve- 

 loped into generative appendix or gills. All the species of 

 Sphfrillo and Armadillo have as far as I know trachese in 

 the exterior branch of all the 5 pairs of pleopodes. This 

 deckplate can appear in very different form and consistance 

 and can give good characters, sexual, as well as special and 

 general. The relation I have used for classification, because 

 it seems to me to be essential, is the existence or complet 



