COLLECTED AT PLYMOUTH IN 1888-89. 147 



calanus elongatus, Boeck, as distinct genera ! [' Proc. Liv. Biol. 

 Soc./ ii, pp. 140, 142.) 



4. DiAS LONGiREMis, LiUjehovg, PL XI, figs. 4 — 6. 



DiAS L0NGIBEMI3, Brady. Monogr. Brit. Copep., i, p. 51, pi. v, 



— — Claus. Freilub. Copepod., p. 193, Taf. xxxiii, figs. 6—14. 



— — Giesbrecht. Freileb. Copep. der Kieler Foehrde, p. 148. 



— — I. C. Thompson. Some Copepoda new to Britain, &c., Proc. 



Liv. Biol. Soc, i, p. 37. 



This species is one of tlie most common near Plymouth. I have 

 taken it in great quantities at all seasons of the year. Giesbrecht 

 remarks that the genus Bias is found very sparingly at Kiel during 

 the early spring months, but that it increases in numbers from July 

 to the autumn. At Plymouth the contrary appears to be the case. 

 On February 20th, 21st, and 22nd, 1889, the Calanidgs taken in the 

 tow-net consisted almost exclusively of this species, and it was abun- 

 dant in gatherings made both before and after these dates. 



A close examination of these specimens leaves me in some doubt 

 as to the distinctness of Giesbrecht's three species, B. longiremis, 

 Lilljeborg; D. Mflosus, and D. discaudatus. According to him the 

 remarkable differences (auffallende Merkmale) between D. longiremis 

 and D. Ujilosus are the presence of spines on the last thoracic segment 

 of the former, and their absence in the latter species ; the shape of 

 the furca, which is much longer in D. longiremis than in D. hifilosus, 

 and the presence of frontal setae in the latter species. B. discaudatus 

 is distinguished principally by the swollen furcal segments of the 

 female and the spermatophores of the male, but in addition to these 

 characteristics there are differences in the fifth pair of feet in the 

 male {vide Giesbrect, loc. cit., Taf. viii, figs. 30, 31, and 32). In 

 my specimens the spines characteristic of Bias longiremis are present, 

 but are not so long as those figured by Giesbrecht ; there are no 

 frontal setee and the feet of the fifth pair are precisely those figured 

 by Giesbrecht for D. longiremis. The difference lies in the furcal 

 segments, the proportions of which are those of B. hifilosus, Gies- 

 brecht and not of B. longiremis. From his drawing of the fifth 

 pair of feet of the male I have no doubt that Brady's figures are 

 taken from B. longiremis, Lilljeborg, though he has overlooked the 

 spines of the last thoracic and abdominal segments. Claus' figure 

 of the fifth pair of feet of the male is undoubtedly taken from B. 

 discaudatus, Giesbrecht (cf. Claus, Freileb. Copepod., Taf. xxxiii, fig. 

 14, and Giesbrecht, loc. cit., Taf. viii, fig. 32). At the same time 

 Claus speaks of the frontal setae characteristic of B. hifilosus. Gies- 

 brecht considers that the varieties in the fifth pairs of feet of the 



