REVISION OF DANIELSSENIA AND PSAMMIS 



47 



differential interference contrast microscope. The terminol- 

 ogy for body and appendage morphology is according to 

 Huys and Boxshall (1991). Abbreviations used in the text and 

 figures are P1-P6 for thoracopods 1-6; exp(enp)-l (-2,-3) to 

 denote the proximal (middle, distal) segment of a ramus. 

 Body length was measured from the base of the rostrum to 

 the posterior margin of the anal somite. 



SYSTEMATICS 



Family Paranannopidae Por, 1984 



Genus Archisenia gen. nov. 



Synonymy. Danielssenia Boeck, 1872 (part). 



Diagnosis. Paranannopidae. Body large, slightly fusiform 

 and dorso-ventrally flattened. Rostrum not hyaline, with 2 

 pairs of small sensillae. Somatic hyaline frills minutely den- 

 tate. Female genital double-somite with lateral and ventral 

 sub-cuticular ridge marking original segmentation; genital 

 field with minute copulatory pore and sinusoidal copulatory 

 duct leading to transverse seminal receptacle partly located 

 anterior to genital slit; P6 with 1 outer plumose seta and 2 

 minute spiniform elements. Pseudoperculum hyaline with 

 dentate margin. Caudal rami slightly divergent and slightly 

 longer than broad. Female antennule 6-segmented; aes- 

 thetasc on segment 4; distal 2 segments with heavily pectinate 

 spines. Antennary exopod 3-segmented with armature for- 

 mula [2-1-3]. Mandibular coxa elongate, with blunt teeth on 

 gnathobase; basis with 4 setae; endopod 1 -segmented; exo- 

 pod 2-segmented. Maxilliped subchelate with 1 large and 1 

 small seta on syncoxa; basis with naked seta on palmar 

 margin, endopodal claw with 2 accessory setae. PI exopod 

 3-segmented, exp-3 with distal outer spine longer than middle 

 outer spine; endopod longer than exopod, 2-segmented, 

 enp-2 4.5 times longer than broad, inner seta implanted 

 medially. P2-P4 intercoxal sclerites with spinules or setules 

 on distal margin; rami 3-segmented; exp-1 with inner seta; 

 female P2-P3 enp-2 with small apophysis at outer distal 

 corner. Armature formula of P1-P4 as follows: 



Exopod 



Endopod 



PI 



0.1.023 



1.121 



P2 



1.1.223 



1.1.221 



P3 



1.1.323 



1.1.321 



P4 



1.1.323 



1.1.221 



Female fifth pair of legs not fused medially; exopod and 

 baseoendopod separate, each with 5 setae, inner seta on 

 exopod well separated from remaining 4 setae. 



Male with sexual dimorphism on antennule, PI, P2 endo- 

 pod, P3 endopod, P5, P6 and in genital segmentation. 

 Antennule 9-segmented, subchirocer; segment 6 very swol- 

 len, with aesthetasc. PI inner basal spine less strongly devel- 

 oped, segments of rami more slender and spinule rows on 

 outer margin of endopod much smaller. P2 enp-1 larger, with 

 inner seta transformed into a non-articulating process; enp-2 

 without inner seta, outer distal corner attenuated into a long 

 apophysis reaching far beyond the distal border of enp-3; 



enp-3 with distal outer spine partially fused to segment, much 

 shorter and stronger than in female, with spinules reduced to 

 coarse teeth, other setae reduced in size. P3 enp-2 with inner 

 distal corner slightly attenuated, outer distal corner attenu- 

 ated into a hook-shaped apophysis. Fifth pair of legs fused 

 medially; baseoendopod and exopod separate with 2 and 5 

 setae, respectively. P6 symmetrical, fused to somite, with 3 

 setae each. 



Type species. As a result of the arguments and analysis put 

 forward below we regard D. stefanssoni Willey, 1920 as a 

 junior synonym of D. sibirica Sars, 1898 and therefore A. 

 sibirica (Sars, 1898) comb. nov. is designated as the type 

 species. 



Other species. None. 



Etymology. The generic name is derived from the Greek 

 prefix archi, meaning first in time and alludes to the primitive 

 position in the family. Gender: feminine. 



Archisenia sibirica (Sars, 1898) comb. nov. 



Synonymy. Danielssenia sibirica Sars, 1898; Danielssenia 

 stefanssoni Willey, 1920. 



Material examined. 



— National Museum of Natural History (Smithsonian Institu- 

 tion), Washington, D.C.: 8 $$ and 1 cf from Point Barrow, 

 Nuwuk Lake, Alaska, U.S.A.; collected by R. Lewis et ai, 

 August 1 1960, bottom sample A974; identified as D. stefans- 

 soni by M.S. Wilson; 1 °. dissected on 13 slides, 1 d" dissected 

 on 7 slides, others preserved in alcohol: reg. no. USNM 

 204769. 



— Naturhistoriska Riksmuseet, Stockholm: 1 $ and 1 cf 

 from East Greenland, Barclay Bay; collected by Jespersen, 

 July 14 1932; identified as D. stefanssoni by K. Lang; 

 preserved in alcohol; reg. no. Cop. 31. 



Description of female. Body slightly dorso-ventrally flat- 

 tened (as for male, Fig. 9B); length 0.97-1.242 mm (x = 

 1.15 mm; n = 7); urosome clearly demarcated from prosome. 

 Cephalothorax rounded anteriorly, widest near posterior 

 margin. Rostrum (Fig. 2A) not hyaline; tapering anteriorly; 

 with 2 pairs of sensillae. Free prosomites each with a dorsal 

 row of spinules and some sensillae near posterior margin; 

 hyaline frill of prosomites minutely dentate. All urosomites 

 (Fig. 1A-B) with lateral row of spinules; first to third 

 urosomites with dorsal row of spinules, 2 rows dorsally on 

 genital somite; ventral spinule row on posterior border of 

 genital double-somite and succeeding urosomites, slightly 

 anterior to lateral rows. Genital double-somite (Fig. 1A-B) 

 with lateral and ventral subcuticular ridge. Genital field (Fig. 

 1C-D) with minute copulatory pore posterior to genital slit; 

 copulatory duct sinusoidal (Fig. ID) leading to single, trans- 

 versely elongate seminal receptacle located at level of genital 

 slit; vestigial P6 with 1 plumose seta and 2 spinules (vestigial 

 setae?); paired, blind ending, cuticular invaginations poste- 

 rior to genital field (Fig. 1C). Hyaline frill of urosomites 

 minutely dentate, that of penultimate somite extended to 

 form pseudoperculum (Figs. IB, 8C). Anal somite deeply 

 incised. Caudal rami (Figs. IE, 5F, 8C) tapering posteriorly, 

 slightly longer than broad, with short spinule row medially on 

 lateral margin and a latero-ventral spinule row on distal 

 margin which also has a large pore near ventral outer corner 

 (Fig. IE); seta I minute (Fig. 5F); setae IV & V well 



