118 



Bemærkninger. — Nærværende Phj'llopode er 

 allerede i Aaret 1785 beskrevet af 0. Fr. Muller 

 som Lynceus hracliyurus. At den senere som Hedcssa 

 SiéboJdi af Liévin opforte Form er identisk med 

 Miiller's Art, er først sikkert bleven constateret af 

 Grube. Af de fra andre Verdensdele opforte Arter 

 synes de 2 nordamerikanske, L. Goiddii Baird og L. 

 mucronala Packard at komme vor Art meget nær. 

 Derimod afviger de 2 australiske Arter, L. madeayana 

 King og L. Tatei Brady, som jeg begge har liavt 

 Anledning til at undersoge noiere, meget bestemt i 

 Henseende til Formen af Rostrum. Af den euro- 

 pæiske Art har Gfrube givet en meget udførlig og 

 indgaaende Beskrivelse, ligesom han ogsaa forst har 

 givet nærmere Oplysninger om dens eiendommelige 

 Larvetidvikling. 



Beskrivelse af Huimeu. 



Skallen har hos de storste af mig indsamlede 

 Exemplarer en Længde af 4V2 mm. og en Hoide af 

 3,80 mm. Den bestaar, som hos Limnadia, af 2 

 tydeligt begrændsede Valvler, forbundne med hin- 

 anden langs Dorsalsiden. Forbindelsen er temmelig 

 ulig den hos Limnadia og gjor niere Indtryk af at 

 være en virkelig Laas, i Lighed med hvad man 

 finder hos Ostracoderne. Medens nemlig hos den 

 sidstnævnte Slægt de 2 Valvler støder sammen oven- 

 til vinder en spids Vinkel, danner de her, for de for- 

 binder sig med hinanden, en pludselig Omboining 

 eller Fold, hvorved Forbindelsen mellem begge kom- 

 mer til at ligge i Bunden af en dyb Fivre, der 

 strækker sig langs Rygsiden af Skallen (se Tab. 

 XVm, Fig. 7 og 8). Seet fra Siden (Fig. 6), har 

 Skallen en noget uregelmæssig rundagtig Form, med 

 den .storste Høide, der falder over den forreste Del, 

 næsten ligesaa stor som Længden. Dorsalkanten er 

 kun meget svagt buet og skraat heldende bagtil, 

 forbindende sig med den bagre Kant uden nogen 

 tydelig Vinkel. Fortil er der en noget fremsprin- 

 gende, men afrundet Forhoining, hvor Dorsalkanten 

 forbinder sig med Forkanten. De frie Kanter af 

 Valvlerne danner en fuldkommen jevn og uafbrudt 

 Bue, som dog er noget fladere fortil, hvorfor ogsaa 

 Skallen viser sig fortil ligesom stumpt afkuttet, 

 medens den bagtil er mere jevnt afrundet. Seet 

 ovenfra (Fig. 8), viser Skallen sig overordentlig stærkt 

 buget, bredt ægformig, med den storste Brede bag 

 Midten, og noget mere afsmalnende fortil end bag- 

 til, hvor den pludselig indsnævres til en kort stump 

 Fremragning. Naar, som sædvanlig er Tilfældet, 

 Valvlerne er halvt aabne (se Fig. 2), svnes Skallen, 

 ovenfra eller nedenfra seet, end bredere og næsten 

 fuldstændig kugleformig. Dreies Skallen saaledes. 



at the point. Colour, a dark olive-green. Length 

 of the shell, up to 4\'2 mm. 



Remarks. ~ This Phjdlopod was described by 

 0. Fr. MtiUer as early as the year 1785, under the 

 name of Lyncens brachyurus. That the form subse- 

 quently described by Liévin as Hedessa Sieboldi is 

 identical with Miiller's .species, was fii'st proved 

 with certainty b}' Grube. Of the .species described 

 from other quarters of the globe, the 2 North Ame- 

 rican species, L. Gouldii, Baird, and L. mucronafa, 

 Packard, seem very much to resemble our species. 

 On the other hand, the two Australian species, L. 

 madeayana, King, and L. Tatei, Brady, both of 

 which I have had the opportunity of examining 

 minutely, diflPer very decidedly in regard to the 

 form of the rostrum. Grube has given a very 

 detailed description of the European species, and 

 was also the first to give any exact information 

 about its peculiar larval development. 



Description of tlie Female. 



In the largest of the specimens collected by 

 me the shell has a length of 4V2 mm. and a height 

 of 3.80 mm. It consists, as in Limnadia, of 2 dis- 

 tinctly defined valves, connected with one another 

 along the dorsal side. The connection is rather 

 unlike that in Limnadia, and gives more the impres- 

 sion of an actual hinge, such as is found in the 

 Ostracods; for while in the latter genus the 2 valves 

 meet above in an acute angle, they here, before 

 joining one another, form a sudden bend or fold, 

 thereby causing the connection between them to lie 

 at the bottom of a deep furrow, which extends along 

 the dorsal side of the shell (see PI. XVIII, figs. 7 

 and 8). Seen from the side (fig. 6), the shell has a 

 somewhat irregular, rounded form, with the greatest 

 height, which falls over the foremo.st part, almost 

 equal to the length. The dorsal margin is only , 

 very slightly curved, and inclines obliquely back- f 

 wards, uniting with the hind margin without any 

 distinct angle. In front there is a very projecting 

 but rounded prominence, where the dorsal margin 

 unites with the anterior. The free edges of the 

 valves form a perfectly even and uninterrupted 

 curve, which, however, is rather flatter in front, 

 thus causing the shell to appear anteriorly as if 

 bluntly truncated, while at the back it is more 

 evenly rounded. When seen from above (fig. 8), the 

 shell appears to bulge very much, and is broadly 

 ovate, with the greatest breadtli behind the middle, 

 and rather more tajDcring in front than behind, 

 where it suddenly contracts into a short, blunt pro- 

 jection. When, as is usually the case, the valves 

 are half open (see fig. 2), the shell, when seen from 

 above or below, appears still broader and almost 

 spherical. When the shell is turned in such a way J 



