of the Fishery Board for Scotland. 293 
Lynceus quadrangularis, Miiller. 
1776. Lynceus quadrangularis, Miller, Zool. Dan. Prod., p. 199, No. 2398. 
1850. Alona quadrangularis, Baird, Brit, Entom, ) D: 131, pl. xvi. fig. 4. 
1860. Lynceus affinis, Leydig, Naturges. der Daph, p- 223, pl. xi. figs. 68, 69. 
1867. Lynceus quadrangularis, Nor. and Brady, Joc. cit., e B77, Pe ae fig. 5. 
1884. Alona quadrangularis, Herrick, loc. cit., p. 97, pl. E , figs. 1 
A widely distributed and common species, with which Alonopsis elongatus 
has probably been included, though this latter species is easily distinguished 
by its greater size and by the form of the post-abdomen, and the armature 
of the terminal claws of the same. 
Lynceus costatus (G. O. Sars). 
1862. Alona costata, G. O. Sars, op. cit., Andet Bidrag., p. 38. 
1867. Lynceus costatus, Nor. idk Brady, loc. cit., p. 379, pl. xviii. fig. 2; pl. 
ext, {0 7. 
1884. Alona costata, Herrick, loc. cit., p. 97. 
This species is considered by Herrick as a not very satisfactory one, 
being “founded practically upon the absence of the eighth seta of the 
antenne.” The post-abdomen is short, moderately broad, and of nearly 
equal breadth as far as thesuperior marginal spines extend, and the 
termination of the superior margin is produced to form a distinct angle. 
Lynceus guttatus (G. O. Sars). 
1862. Alona guttata, G. O. Sars, op. cit., Andet Bidrag., p. 38 
1867. Lynceus guttatus, Nor. and Brady, Joc. cit., p. 380, pl. xviii. fig. 6 ; 
pio xxt, fig. 10. 
1884. Alona guttata, Herrick, Joc. cit., p. 94. 
This comes near to the last, but the post-abdomen is shorter and more 
hollowed out on the superior margin immediately in front of the marginal 
spines. The surface of the carapace is frequently ornamented by cellular or 
pit-like impressions it is also rather smaller than ZL. costatus. 
Alonella, Sars. 
Alonella exigua, (Lilljeborg). 
1853. Lynceus exiguus, Lillj., De Crust. in Scania Occurr., p. 79, pl. vii. figs. 9, 
10. 
1854. Lynceus excisus, Fischer, Bull. de Soc. Imp. des Nat. de Moscou, p. 428, 
pl. ii. figs. 11-14. 
1862. <Alonella eacisa, G. O. Sars, op. cit., Andet Bidrag., p. 52. 
1867. Lynceus exiguus, Nor. and Brady, loc. cit., p. 384, pl. Vide HE esl eX. 
fig. 3. 
1884. aaa excise and exigua, Herrick, loc. cit., pp. 108-105, pl. EH, fig. 6 ; 
pl. G, figs. 10, 11. 
The two forms here referred to are by some authors considered as 
distinct species, but so far as I can make out from the descriptions and 
figures of the authors cited, the chief difference between A. exigua and 
A. excisa is, that in the first, the carapace is smooth or nearly so, whereas 
in the second it is distinctly reticulated and marked between the reticula- 
tions by distinct and close-set striz. This difference does not seem to be 
of sufficient importance to be specific. The post-abdomen, so far as I can 
make out from the specimens examined, is similar in form in both, the 
antenne also of both are similar. I have therefore included both in 
Lilljeborg’s species. 
Alonella nana (Baird). PI. ii. fig. 6. 
1850. Acroperus nanus, Baird, Brit. Entom., p. 130, pl. xvi. fig. 6 
1860. Lynceus nanus, Leydig, Naturges. der. Daphn., p. 228. 
1862. Alonella pygmea, G. 0. Sars, op. cit., Andet Bidrag., p. 48. 
1867. ee nanus, Nor. and Brady, loc. cit., p. 396, pl. xviii. fig. 8; pl. xxi. 
1884. Mina pygmeea, Herrick, loc. cit., p. 105, pl. H, fig. 7. 
