DK. H. J. HANSEN ON BATHTNOMUS GiaANTEFS. 21 



Isopodes, se composent de 6 articles. Le premier est immobile, 

 interrompu eu dessus a la base des antennules, et forme en 

 arriere un prolongement triaugulaire entre les parties laterales 

 du eljpeus et la partie iaferieure de la region cephalique. Le 

 deuxieme anneau est mobile . . ." These statements and tbe 

 figure mentioned are partly incorrect. In 'Isopoden, Cumaceen, 

 und Stomatopoden der Plankton-Expedition ' I have written 

 (p. 4) : " Bei Asellota hat der Stiel der Antennen 6. Glieder (ein 

 Charakter, der bei Mysidce verce sich wieder findet) uud oftmals 



ein rudimentares Squama auf dem 3. Gliede Bei alien 



andern Isopoden . . . . ist der Stiel der Antennen hochstens 

 5-gliedrig (das 1. Glied ist mit dem Kopfe vereinigt), ohne 

 Squama, . . ." But I discover now that BatJiynomus disagrees 

 with these statements of Bouvier and of myself : the antennal 

 peduncle consists certainly of six joints, hut all are movable. 

 What has been considered by Bouvier as the first, immovable 

 joint is a portion of the head (PI. 4. fig. 9, a), not marked ofE 

 posteriorly as in his fig. 4 ; furthermore he has overlooked the real 

 first joint. This joint (PL 4. fig. 9, 1) is a rather narrow longi- 

 tudinal strip of hard chitine, situated on the lower side of the head 

 outside the second joint ; when I turned the peduncle of the 

 antennae backwards and inwards, this basal joint was very con- 

 spicuously moved, and the faculty of movement indicates the 

 presence of an articular membrane between the hard strip and 

 the skeleton of the head. My fig. 9 shows an anteriorly narrow, 

 posteriorly broad articular membrane between this basal joint and 

 the second one (2), and besides a well-developed articular 

 membrane between the posterior margin of the second joint and 

 the head. The position of the first joint is quite as in Eurycope 

 (comp. fig. 3 6 on pi. 20 in my report on the Crustacea in 

 ' Dijmphna-Togtets zoologisk-botaniske Udbytte,' Kjobenhavn, 

 1887) and other Asellota, but it is proportionately considerably 

 shorter. The third and following joints have been correctly 

 described and figured by Bouvier. 



After the discovery of the basal movable joint in BatJiynomus, 

 I examined the antennae in Girolana elongata, H. M.-Edw., 

 C. lorealis, Lilljeb., and G. Cranchii, Leach (three species repre- 

 senting different groups of that extensive genus), and I was now 

 able to find the same basal joint at the outer margin of the 

 following one. It is especially well developed in G. elongata, but 

 also distinct in the two other species ; when the lower surface of 



