118 



Bemærkninger. — Nærværende Phyllopode er 

 allerede i Aaret 1785 beskrevet at' 0. Fr. Muller 

 som Lynceiis hrachyiirua. At den senere som Ucdcssa 

 Sieholdi af Liévin opforte Form er identisk med 

 Muller's Art, er forst sikkert bleven constateret af 

 Grnbe. Af de fra andre Verdensdele opforte Arter 

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

 nmcronata Packard at komme vor Art meget nær. 

 Derimod afviger de 2 australiske Arter, L. madeayana 

 King og L. Ta fei Brady, som jeg begge har Lavt 

 Anledning til at midersøge nøiere, meget bestemt i 

 Henseende til Formen af Rostrum. Af den euro- 

 jtæiske Art har (Irube givet en meget iidforlig og 

 indgaaende Beskrivelse, ligesom han ogsaa forst har 

 givet nærmere Oplysninger om dens eiendommelige 

 Larveudvikling. 



Beskrivelse af Hiinnen. 



Skallen har hos de storste af mig indsamlede 

 Exemplarer en Længde af 4V'2 mm. og en Hoide af 

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

 tydeligt begrændsede Valvler, forbundne med hin- 

 anden langs Dorsalsiden. Forbindelsen er temmelig 

 ulig den hos Limnadia og gjor mere Indtryk af at 

 være en virkelig Laas, i Lighed med hvad man 

 finder hos Ostracoderne. Medens nemlig hos den 

 sidstnævnte Slægt de 2 Valvler steder sammen oven- 

 til under 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 Fure, der 

 strækker sig langs Rygsideu af Skallen (se Tab. 

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

 Skallen en noget uregelmæssig rundagtig Form, med 

 den storste Hoide, der falder over den forreste Del, 

 næsten ligesaa stor som Længden. Dorsalkanten er 

 kun meget svagt Ijuet og skraat heldende bagtil, 

 forbindende sig med den bagre Kant uden nogen 

 tydelig Vinkel. Fortil er der en noget fremspi-in- 

 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, In'edt ægformig, med den storste Brede liag 

 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), synes 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^/s mm. 



Remarks. — This Phyllo]Kid was described by 

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

 name of Lyncens hrachyurus. That the form subse- 

 quently described by Liévin as Hedessa Sieholdi is 

 identical with Miiller's species, was first proved 

 with certainty by Grrube. Of the species described 

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

 rican species, L. Goiddii, Baird, and L. mucronaki, 

 Packard, seem very much to resemble our species. 

 On the other hand, the two Australian species, L 

 macleaycmn, King, and L. Tatei, Brady, lioth of 

 which I have had the opportunity of examining 

 minutely, differ very decidedly in regard to the 

 form of the rostrum. Grube has given a ver^- 

 detailed description of the European species, and 

 was also the first to give any exact information 

 about its jieculiar larval develojmient. 



Desi-rii»tioii 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 Ijend or fold, 

 thereby caiising 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 foremost part, almost 

 equal to the length. The dorsal margin is only 

 very slightly curved, and inclines obliquely liack- 

 wards, uniting with the hind nmrgin without any 

 distinct angle. In front there is a very ])roiecting 

 ln;t 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 cau.sing 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 breadth behind the middle, 

 and rather more tapei'ing 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, a])pears still broader and almost 

 spherical. When the shell is turned in such a way 



