16 
Heterocalanus medius Wolfenden, may be the species described by Kroyer 1848—49 
as Calanus cristatus. Two figures of the forehead of Krover’s species are given by GrEsBRECHT 
in ‘Fauna und Flora des Golfes von Neapel’ (pl. 6, figs. 14—15). 
Genus Undinula nom. nov. 
= Undina Dana, 1847. A name preoccupied by GOULD, (Aves) 1836 and Munst., (Pisces) 1842. 
GIESBRECHT 1893, combined the genus Uzdzma Dana, with Ca/anus Leach, and with 
the exception of Sars, subsequent workers adopted this plan. Sars 1902, p. 8, points out that 
the structure of the fifth feet of the male of Usdzna differs considerably from the males of true 
Calanus, and that the genera ought properly to be kept apart. Very little examination of the 
fifth feet of the males of the types of the two genera is required to shew that Sars view is 
the correct one. There is no similarity between the left fifth foot of the male of Calanus 
finmarchicus, and that of the male of Uxdina vulgaris. The males of Dana’s Undina have 
the last joint of the exopodite of the left fifth foot developed into a well defined prehensile organ. 
The generic name used by Dana had been established for a genus of birds previous 
to its adoption by that author and Uzdznula has, therefore, been substituted for Undzna in 
the present report. 
The females of Unxdinula differ very little in the structure of the appendages from typical 
Calanus, the only noticeable distinction is an incomplete division of the eighth and ninth joints 
of the antennules. There are five pairs of bi-ramose feet, all adapted for swimming, and each 
branch is three-jointed. The males are very easily recognised by the structure of the fifth pair 
of feet. The foot of the right side is bi-ramose and each branch is three-jointed. The left foot 
has the exopodite considerably elongated and its last joint is converted into a powerful bi-ramose 
prehensile organ. The endopodite of the left foot may be entirely absent as in Undinula 
vulgaris, or very rudimentary, consisting of one small joint, asin Undinula darwint and Undinula 
carolt. Vhere are at present three species belonging to this genus and they were all noted in 
the ‘Siboga’ material. 
1. Undinula vulgaris (Dana). 
Undina vulgaris Dana, 1849, pp. 17, 18, 22. 
Undina vulgaris Brady, 1883, p. 53, pls. XV & XVIII. 
Calanus vulgaris Giesbrecht, 1893, p. 92, pls. 6, 7, 8. 
Undina vulgaris T. Scott, 1893, p. 44. 
Calanus vulgaris Giesbrecht, 1895, p. 248. 
Calanus vulgaris Giesbrecht & Schmeil, 1898, p. 17. 
Calanus vulgaris 1. C. Thompson, 1900, p. 275. 
Calanus vulgaris Cleve, 1901, p. 5. 
Calanus vulgaris A. Scott, 1902, p. 400. 
Calanus vulgaris Thompson & Scott, 1903, p. 242. 
Calanus vulgaris Cleve, 1903, Pp. 357. 
Calanus vulgaris Cleve, 1904, p. 186. 
Calanus vulgaris Wolfenden, 1905(a), p. 994, pls. XCVI & XCVII. 
Undina vulgaris Sars, 1905(a), p. 2. 
16 
