of the Fishery Board for Scotland. 
293 
Lynccus quadrangularis, Miiller. 
1776. Lynceus qtiadrangtdaris, Miiller, Zool. Dan. Prod., p. 199, No. 2393. 
1850. Alona quadrangularis, Baiid, Brit. Entoni., p. 131, pi. xvi. fig. 4. 
1860. Lynceus ajfinis, Leydig, Naturges. der Daph, p. 223, pi. xi. figs. 68, 69. 
1867. Lynccus quadrangular is, Nor. and Brady, loc. cit.-, p. 377, pi. xxi. fig. 5. 
1884. Alona quadrangularis, Horrick, loc. cit, p. 97, pi. E, figs. 1, 2. 
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 costatiis (G. 0. Sars). 
1862. Alo7ia costata, G. 0. Sars, op. cit, Audet Bidrag., p. 38. 
1867. Lynceus costatus, Nor. and Brady, loc. cit., p. 379, pi. xviii. fig. 2 ; pi. 
xxi. fig. 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 
antennae." The post-abdomen is short, moderately broad, and of nearly 
equal breadth as far as the superior marginal spines extend, and the 
termination of the superior margin is produced to form a distinct angle. 
Lynceus guttatus (G. 0. Sars). 
1862. Alona guttata, G. 0. Sars, op. cit., Andet Bidrag., p. 38. 
1867. Lynceus guttatus, Nor. and Brady, loc. cit, p. 380, pi. xviii. fig. 6 ; 
pi. xxi. fig. 10. 
1884. Alona guttata, Herrick, loc. 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 L. costatus. 
Alonella^ Sars. 
Alonclla exigua (Lilljeborg). 
1853. Lynceus exiguus, Lillj., De Crust, in Scania Occurr., p. 79, pi. vii. figs. 9 
10. 
1854, Lynceus excisus, Fischer, Bull, de Soc. Imp. des Nat. de Moscou, p. 428, 
pi. iii. figs. 11-14. 
1862. Alonclla cxcisa, G. 0. Sars, op, cit, Andet Bidrag., p. 52. 
1867. Lynceus exiguus, Nor. and Brady, loc. ext., p. 384, pi. xviii. fig. 3; pi. xxi. 
fig. 3. 
1884. Alonella exdsa and exigiui, Herrick, loc. cit, pp. 103-105, pi. E, fig. 6 ; 
pi. 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 
ligures of the authors cited, the chief difference between A. exigua and 
A. exdsa 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 strise. 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 
antenna? also of both are similar. I have therefore included both in 
Lillj eborg's species. 
Alonella nana (Baird). PI. ii. fig. 6. 
1850. Acroperus nanus, Baird, Brit. Entom., p. 130, pi. xvi. fig. 6. 
1860. Lynceus nanus, Leydig, Naturges. der. Daphn., p. 228. 
1862. Alonella pygmcea, G. 0. Sars, op. cit, Andet Bidrag., p. 48. 
1867. Lynceus nanus, Nor. and Brady, loc. cit., p. 396, pi. xviii. fig. 8 ; pi. xxi. 
fig. 8. 
1884. Alonella pygmcea, Herrick, loc. cit., p. 105, pi. H, fig. 7. 
