122 



af Hovedet opover, vil man helt bagtil, i uogen 

 Afstand fra den tværgaaende Siitur, der skiller Ho- 

 vedet fra Nakkesegmentet, bemærke en liden grube- 

 formig Fordybning (Fig. 11, x), der constant fore- 

 kommer ber hos alle Individer, Ijaade Hanner og 

 Hunner. Ifolge sin Plads maa denne Grrube nær- 

 mest ansees for homolog med Fastheftningsorganet 

 hos Limnadia, skjondt det er lidet troligt, at denne 

 ubetydelige Grrube kan her fungere som et saadant 

 Organ. 



Forste Par Folere (Fig. 11, a\ Fig. 2), som er 

 fæstede til hver Side af Hovedets ventrale Del, 

 umiddelbart foran Basis af Overlæben, er meget 

 smaa og af noget kolledannet Fonn. De bestaar 

 hver af et kort Skaft og en noget buet, i sit ydre 

 Parti fortj-kket Endedel, der fortil er tæt besat med 

 delicate Lugtepapiller (Fig. 2 a), af et lignende Ud- 

 seende som hos Limnadia. Disse Følere er til en 

 vis Grad bevægelige ved Hjælp af en Del smaa 

 Mu.skler, som passerer til dem fra Hovedets Inte- 

 gument. 



Andet Par Folere, eller Aarerne (Fig. 3), ud- 

 springer, som hos Limnadia, med en bred Basis fra 

 Hovedets Sider, umiddelbart under den bagre, mest 

 fremspringende Del af Fornix. De bestaar af de 

 samme Dele som hos Limnadia, nemlig et tykt, 

 cylindriskt Skaft, og 2 Grene; men disse sidste er 

 her paa langt nær ikke saa stærkt forlængede som 

 hos hin Slægt. Skaftet, hvis basale Del synes at 

 være fuldstændig ubevægelig, er derimod paa Midten 

 meget boieligt og her delt i flere korte, tildels ufuld- 

 stændigt sondrede Led, medens dets 3'dre Trediedel 

 danner et enkelt Led for sig. Fra Basaldelen ud- 

 gaar bagtil et Antal af omkring 5 stærke nedad- 

 rettede Fjærborster, og i Forkanten af det yderste 

 af de mediane Led er der en Del grove Pigge, ord- 

 nede i en TvæiTad. En lignende Tværrad af Pigge 

 findes ogsaa ved Enden af Skaftet fortil. Grenene 

 er neppe længere end Skaftet og omtrent af ens 

 Storrelse, eller den bagre ubetydeligt længere end 

 den forreste. De er begge delte i et stort Antal 

 (fra 15 til 18) korte Led, der dog ved Basis af Gre- 

 nene er meget utydeligt sondrede. Ethvert Led har 

 i Bagkanten en enkelt lang Svømmeborste, og paa 

 den forreste Gren har de fleste Led endnu hvert en 

 enkelt stærk Pig i den modsatte Kant. Sidste Led 

 har paa den bagre Gren 2 Svommebørster, paa den 

 forreste desforuden en Pig. Naar Aarerne er i 

 Hvile, lægges de almindeligvis langs ad Siderne af 

 Hovedet, umiddelbart bag dettes laterale Kjole. De 

 fra Hovedets Integument til Aarerne gaaende Musk: 

 ler er meget kraftige og fæster sig alle ved det 

 midterste bøielige Parti af Skaftet. I dettes ydre 

 Del sees andre Muskler, der virker paa enhver af 

 Grenene. 



the dorsal margin of the head xipwards, there 

 is observable, at the very back, at some distance 

 from the transverse suture, which separates the 

 head from the cervical segment, a small pit-like 

 depression (fig. 11, a;), which occurs invariably in all 

 specimens, both males and females. From its place, 

 this pit must probably be regarded as homologous 

 to the organ of attachment in Limnadia, although 

 it is almost incredible that this insignificant hollow 

 can here act as such an organ. 



Tlie 1st pair of antennæ (fig. 11, a^, fig. 2) which 

 are attached to the sides of the ventral portion of 

 the head, immediately in front of the base of the 

 labrum, are very small, and of a somewhat clavate 

 form. They each consist of a short scape, and a 

 somewhat curved terminal part, thickened in its 

 outer poi'tion, and thickly set in front with delicate 

 olfactory papillæ (fig. 2 a), of an ajjpearance similar 

 to those in Limnadia. These antennæ are movable 

 to a certain extent bj' the aid of several small 

 muscles passing to them from the integviment of 

 the head. 



The second pair of antennæ, or the oars (fig. 3) 

 issue, as in Limnadia, with a broad base from the 

 sides of the head, immediateh' below the hinder, 

 most projecting part of the fornix. They consist of 

 the same parts as in Limnadia, namely a thick, 

 cylindrical scape, and 2 rami; bvit the latter are 

 here not nearly so much elongated as in the before- 

 mentioned genus. The scape, of which the basal 

 part appears to be quite immovable, is, on the 

 other hand, very flexible in the middle, and is here 

 divided into several short, to some extent imper- 

 fectly defined joints, while its distal third part 

 forms a single joint by itself. From the basal part 

 there issue at the l^ack about 5 strong, downward- 

 pointing plumose setæ, and on the anterior margin 

 of the most distal of the median joints, there are a 

 number of coarse spines arranged in a transverse 

 row. A similar transverse row of spines is also 

 foimd at the end of the scape in front. The rami 

 are scarcely longer than the scape, and are of 

 almost equal size, the hind one being very slightly 

 longer than the front one. They are both divided 

 into a great number (from 15 to 18) of .short joints, 

 which, however, are very indistinctly defined at 

 the base. On the hind margin of each joint, there 

 is a single long natatory bristle, and on the front 

 I'amus, most of the joints have yet another single, 

 strong spine on the opposite margin. On the hind 

 ramus there are 2 natatory bristles on the last 

 joint, and on the front ramus, a spine as well. 

 When the oars are at rest, they generally lie 

 along the sides of the head, immediately behind its 

 lateral keel. The muscles running from the integu- 

 ment of the head to the oars are very powei'ful, 

 and are all attached to the middle, flexible part of 



