studies on marine Oslracods 705 



Second antenna: — The b-bristle on the first joint of the endopodite had in 

 one specimen two, in the other three long hairs. 



Sixth limb: — The endopodite had two bristles, one of which was rather short. 

 Exopodite: The first joint had one short dorso-distal bristle and one rather short bristle at 

 about the middle of the ventral side. 



Are we concerned here with two closely related forms, which were confused by G. \V. 

 MtJLLER, 1906 a, or is C. spinirostris a species with a relatively great amplitude of variation? 



In answering this question the following remark of G. W. MUller, 1906 a, p. 105, has 

 a certain interest: ,, $ von liber 1,4 imd S von fiber 1,3 fanden sich nur in Station 32 — 55, wo die 

 Thiere iiberhaupt im Durehschuitt groBer." In the samples investigated by this writer the large 

 and small specimens were thus not mixed up together Cj[uite without any principle; on the 

 contrary, at the sixteen stations at which large specimens were caught no small specimens were 

 found, nor were any large specimens found at the 36 stations where the plankton samples con- 

 tained small specimens. The stations in question, nos. 32 — 55, are situated in the Atlantic 

 from lat. 24" N. and lat. 2° N. ; the depths are only known in two cases, 42 S. = 550 — 250 m. ; 

 48 S b = 280 — 130 m. To judge from the latter statements it does not seem probable that this 

 difference in size between the specimens investigated is due to external conditions. It is also 

 to be noted that at S. A. E., PI. Station 4 b no small specimens were found, and that no large 

 specimens were found at those stations of this expedition from which the small specimens de- 

 scribed by me above came. 



G. W. MOller, in his work of 1906 a just mentioned, put forward the assumption that 

 C. porrecta C. Cl^AUS was a synonym of C. spinirostris. ,,Ich halte C. porrecta ClaUS nur fur 

 gestreckte Individuen von C. spinirostris.'' (The identification was not based on a re-examination 

 of C. Claus's original material, as is shown by a statement on p. 105 in the work quoted.) It 

 is certain that these two forms are very closely related to each other. According to the description 

 and figures C. porrecta differs from C. spinirostris chiefly in the following characters: Length 

 of shell: 1,6 mm. (this statement, like, as a matter of fact, the whole description of the shell, 

 certainly refers to female specimens). Male first antenna: The a-bristle is relatively short, 

 reaching only to about the boundary between the first and second joints of this limb. E-bristle: 

 ,,.... mit sehr zahlreichen, wohl 40 — 50 Paaren von Hiikchen besetzt, von denen die 14 — 16 

 distalen Paare viel dicker und dichter gestellt sind, die nach der Basis zu folgenden in weiteren 

 Zwischenraumen stehen und zu Stachelborsten werden." (The b-bristle on the first endopodite 

 joint of the male second antenna is not mentioned or reproduced by this writer.) 



If we assume that C. Cl.\us made a mistake in observation (which does not seem to me 

 improbable on account of the uncertainty that often characterizes the statements as to details 

 given by this writer) and there was not a double but only a single row of spines on the e-bristle 

 of the male first antenna proximally of the fourteen to sixteen distal pairs of spines, then the 

 agreement between the information given by this writer for C. porrecta and G. \X. Mt'LLER's 

 description of C. spinirostris, 1906 a, becomes almost c()m]ilete. Tlie latter writer gives no 

 information as to the a-bristle on the male first antenna. The specimens investigated by me 

 from S. A. E., PI. station 4 b agreed in this respect with C. Cl-Ais's statement in the case of 



Zoolotf. bidras, Uppsjila. Suppl.-IM. I. ^J 



