REVISION OF DANIELSSENIA AND PSAMM1S 



75 



abdominal somites (ornamentation) and caudal rami (shape). 



Re-examination of P. longisetosa has revealed a number of 

 features that were overlooked or misinterpreted in earlier 

 descriptions. In many cases these observations have shown an 

 astonishing similarity in the detailed structure of the cephalic 

 appendages between P. longipes and the type species. 



The rostrum is not hyaline (Fig. 22A); the anterior pair of 

 sensillae is enlarged. In the male the antennule is 

 9-segmented (Fig. 22A) and the segmental pattern is homolo- 

 gous to that of Archisenia. 



Mandible (Fig. 21A-B). The gnathobase has similar multi- 

 cuspidate teeth and 2 pinnate setae. The basis has 4 setae; the 

 ornamentation of these setae shows that it is either the 

 proximalmost or following seta that is missing in P. longipes. 

 Both species have the same armature on the rami. 



Labrum (Fig. 22B) with 1 large, median and a pair of 

 smaller secretory pores on the anterior surface, and long 

 spinules around the distal margin. 



The detailed structure of the maxillule and maxilla is 

 exactly the same as in P. longipes, including the presence and 

 position of tubular setae and the modifications of the maxillu- 

 lary coxal endite. 



The maxillipedal syncoxa has been invariably described as 

 possessing a single, very large, spinulose seta, corresponding 

 to the posterior seta in P. longipes; the smaller, setulose, 

 anterior seta in this species is further reduced to a minute, 

 pinnate spine in P. longisetosa (arrowed in Fig. 21C) and 

 approaches the length of the largest ornamental spinules, the 

 reason why it had been overlooked in previous descriptions. 



The sexual dimorphism on the P2 endopod includes modi- 

 fications of the middle and distal segments (Figs 21D-E). The 

 anterior, spinous apophysis on the outer margin of the 

 proximal segment is not a sexually dimorphic feature since it 

 is also found in female specimens. The middle segment is 

 drawn out into a large apophysis not reaching to the end of 

 the distal segment and provided with an anterior secretory 

 pore near the apex; the inner margin has 2 distally serrate 

 setae, the proximal one being slightly displaced to the poste- 

 rior surface; these setae are distinctly longer in the female. 

 The distal segment possesses 4 articulating armature elements 

 corresponding to the 2 inner and 2 terminal setae in the 

 female; the outer spine in the female is modified in the male 

 and replaced by a short, spinous process distally. 



As in P. longipes, the reduced inner terminal seta of P3-P4 

 enp-3, represented by a setule, has been overlooked thus far 

 (arrowed in Figs 21F-G). In the male the outer distal corner 

 of the P3 middle segment is transformed into an acutely 

 recurved process (Fig. 21F); the inner seta on this segment is 

 distinctly longer in the female. 



The fifth legs of both sexes are as in Figs 22E and F, 

 respectively. 



The original segmentation of the female genital double- 

 somite is marked by a transverse chitinous rib dorsally and 

 ventrally (Fig. 22D). The seminal receptacle is relatively 

 small (Fig. 22C); the P6 is represented by 1 plumose seta and 

 1 small spinule in the female; in the male the sixth legs are 

 fused and symmetrical, and bear 2 naked setae on either side 

 (Fig. 22G). 



(v) Amended diagnosis 



Only P. longisetosa and P. longipes are retained in the genus 

 Psammis, which is here redefined. 



Diagnosis. Paranannopidae. Body large, slightly fusiform 

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

 pairs of sensillae, anterior one large. Somatic hyaline frills 

 minutely dentate. Female genital double-somite with lateral 

 and ventral sub-cuticular ridge marking original segmenta- 

 tion; genital field with minute copulatory pore and linear duct 

 leading to transverse seminal receptacle located anterior to 

 genital slit; P6 with 1 plumose seta and 1-2 minute spinulose 

 elements. Pseudoperculum hyaline with dentate margin. Cau- 

 dal rami divergent and longer than broad, tapering slightly. 

 Female antennule 4-segmented; aesthetasc on segment 3; all 

 segments with pinnate setae and spines. Antennary exopod 

 3-segmented with armature formula [2-1-3]. Mandibular 

 coxa elongate, with finely pointed teeth and 2 setae on 

 gnathobase; basis broad with 3-4 setae on distal margin; 

 endopod 1-segmented, equal in length to exopod, with 

 strongly reduced armature; exopod 1-segmented, with 1 

 lateral and 2 distal setae. Maxillule with 2 large comb-like 

 spines and 3 tubular setae on coxal endite; basal endite with 3 

 plumose setae, 1 spine and 1 tubular seta. Maxilla with 

 tubular setae on coxal endites, allobasis and endopod; prae- 

 coxal endite with 2 pinnate spines. Maxilliped subchelate with 

 1 large and 1 small seta (both pinnate) on syncoxa; basis with 

 long plumose seta on palmar margin, endopodal claw with 1 

 accessory seta. PI exopod 3-segmented, exp-3 with distal 

 outer spine longer than middle outer spine; endopod at least 

 as long as exopod, 2-segmented, enp-2 longer than enp-1, 

 inner seta implanted medially. P2-P4 intercoxal sclerites 

 without ornamentation; rami 3-segmented; exp-1 with an 

 inner seta. P2 endopod distinctly longer than exopod; enp-1 

 with outer distal margin attenuated in both sexes; enp-2 with 

 1 inner margin seta and 1 seta implanted on posterior surface. 

 Inner distal seta enp-3 P3-P4 extremely reduced and repre- 

 sented by setule. Armature formula of P1-P4 as follows: 



Exopod 



Endopod 



PI 



0.1.023 



1.121 



P2 



1.1.123 



1.2.221 



P3 



1.1.223 



1.1.321 



P4 



1.1.223 



1.1.221 



Female fifth pair of legs not fused medially; exopod and 

 baseoendopod fused to form a bilobate plate; exopodal lobe 

 with 4-5 setae, endopodal lobe with 5 setae. 



Male with sexual dimorphism in antennule, P2 endopod, 

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

 9-segmented, subchirocer; segment 6 swollen, with aes- 

 thetasc. P2 enp-2 with long outer apophysis not reaching to 

 distal margin of enp-2; enp-3 with outer spine transformed 

 into non-articulating process, distal setae reduced and inner 

 setae enlarged compared to the female. P3 enp-2 with outer 

 distal corner attenuated into a recurved apophysis. Fifth pair 

 of legs not fused medially; endopodal lobe with 2 spines, 

 exopod with 4 setae/spines. Sixth legs symmetrical, fused to 

 somite, with 2 setae each. 



Type species. P. longisetosa Sars, 1910 (by monotypy). 



Other species. P. longipes Becker, 1974. 



Gee (1988a) concurred with Wells' (1967) opinion that a 

 generic distinction between Danielssenia and Psammis on the 

 base of P5 segmentation alone can hardly be justified. 



