of the Fishery Board for Scotland. 
295 
Chydorus, Baird. 
Chydonis glohosus, Baird. 
1850. Chydorus glohosus, Baird, Brit. Entom., p. 127, pi. xvi. fig. 7. 
1867. LyticeiLS glohosus, Nor. and Brady, loc. cit, p. 398, pi. xx. fig. 5. 
1884. Chydonts* glohosus, Herrick, loc. cit, p. 116, pi. F, figs. 1, 2, 3, and 9. 
This fine species does not appear to be very common in Scotland. It 
was obtained by Mr D. Robertson, F.L.S., many years ago in the Paisley 
Canal (where I also found it later on), and in the Hebrides by Eev. A. 
M. Norman. It is recorded from several places both in England and 
Ireland. 
Chydorus sphcericus (Miiller). 
1776. Lynceus sphcericus, Miiller, Zool. Dan. Prod., No. 2392. 
1850. Chydorus bphcericus, Baird, Brit. Entom., p. 126, pi. xvi. fig. 8. 
1884. Chydorus sphcericus, Herrick, loc. ext., p, 116, pi. F. figs. 4, 7, 8, 10. 
Chydorus sphcericus is one of the commonest species of the Lynceidse. 
MonospUuSy G. O. Sars. 
Monospilus tenuirostris (Fischer). PI. i. fig. 1. 
1854. Lynceus tenuirostris, Fischer, Bull, de Soc. Imp. des Nat. de Moscou, p. 
427, pi. M, figs. 7-10. 
1861. Monospilus dispar, G. 0. Sars, op. cit., p. 23. 
1867. Monospilus tenuirostris y Nor. and Brady, loc. cit, p. 403, pi. xix, fig. 2 ; 
pi. xx. fig. 9. 
1884. Monospilus dispar, Herrick, loc. cit, p. 119, pi. i. fig. 21. 
This Lynceid differs from all the other species in having only the larval 
eye present during all stages of growth, and in the ecdysis not being com- 
plete, so that the old shell, instead of being cast off, remains attached to 
the new one, which projects more or less beyond the old. The result is 
that there are in adult specimens the appearance of more or less regular 
growth lines, similar to that observed in some Lamellibranch molluscan 
shells. The head is articulated to the carapace so slightly as to easily 
become detached from it Herrick speaks of it as the " rarest of all 
Entomostraca." He regards it "as a degraded offshoot of the more typical 
stem of the Lynceidse." 
PoLTPHEMIDiE. 
PolyphemuSy Miiller. 
Polyphymus pediculus (Linne). 
1746. Monocidus pediculus, Linne, Faun. Suec, No. 2048. 
1776. Polyphemus occulus, Miiller, Zool. Dan. Prod., No. 2417. 
1850. Polypheinus pediculus, Baird, Brit. Entom,, p. HI, pi. xvii. fig. 1. 
1884. Polyphemus pediculus, Herrick, loc. cit, p. 121, pi. B, figs. 4-6. 
This is a moderately common species, especially in large sheets of water. 
Bythotrephes, Leydig. 
Bythotrephes longimanus, Leydig. 
Bythotrephes longimanus, Leydig. 
Bythotrephes cederstromii, Schoedler. 
Bythotrephes often occurs in considerable abundance ; it is easily dis- 
tinguished by its having an abdominal spine of enormous length. 
