NO. 6.] ACCOUNT OF THE SPECIES. 73 



14. Pseudocalanm pygmceus, n. sp. 

 (PL XXI). 



Specific Characters. 9- Body much shorter and thicker than in the 2 

 preceding species, with the anterior division rather more tumid, and somewhat 

 broader in front than behind, consisting of only 4 distinctly defined segments. 

 Front, as in the type species, with 2 delicate filaments below. Last segment 

 of trunk with the lateral corners rounded off. Tail scarcely more than Vs 

 as long as the anterior division, genital segment short and broad, anal seg- 

 ment scarcely smaller than the preceding one. Caudal rami comparatively 

 short, each with 4 apical setae. Anterior antennae fully as long as the body, 

 and 23-articulate. Posterior maxillipeds comparatively longer than in the 2 

 preceding species, with the terminal part more produced and generally 

 reflexed, Natatory legs very slender, with the apical spine of the outer 

 ramus exceedingly long and narrow. Length of adult female 0'86 mm. 



Remarks. In its external appearance and very small size, this form 

 so strongly recalls Paracalanus parvus Glaus, that at first I believed it to 

 be that species. A closer examination, however, showed it to be in reality 

 very different, and much more nearly related to Pseudocalanus elongatus. 

 Indeed, in all essential structural details, it agrees with this latter form, and 

 ought therefore, in my opinion, to be referred to the same genus, in spite of 

 its very different external appearance. 



Description of the Female. 



The length of the largest specimens found is only 0'86 mm, and this 

 form is accordingly one of the smallest Calanoids known, being even some- 

 what inferior in size to Paracalanus parvus Glaus. 



The general form of the body (see figs. 1 & 2) very much resembles 

 that in the above-named species, the anterior division being rather tumid, 

 and having its greatest width in front of the middle. The cephalic segment 

 is wholly coalesced with the 1st pedigerous one, both forming together a very 

 large segment occupying more than 2 /s of the whole division. Behind it, only 

 3 other segments appear belonging to the trunk, the last 2 segments being 

 likewise united into one. The lateral corners of this segment, as in the 2 



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