in dorsal and lateral view, flat dorsally; an in- 

 conspicuous longitudinal carina ventrally; an 

 inconspicuous dorsal and ventral tooth near tip 

 with tuft of long hairs between upper tooth and 

 apex. Carapace with lower orbital angle bluntly 

 triangular, a strong antennal spine below angle; 

 anterolateral angle broadly rounded and anterior- 

 ly produced. Eyes well developed, not reaching 

 laterally to antennal spine. Antennular peduncle 

 with stylocerite broad, bluntly pointed; antero- 

 lateral angle of basal article produced forward, 

 rounded ; third article longer than second ; upper 

 antennular flagellum with 7-10 fused joints; short 

 ramus with 2 or 3 joints. Antennal scale broadly 

 oval, outer margin a little convex, terminal tooth 

 small, exceeded by lamella; antennal peduncle 

 reaching beyond middle of scale. 



First leg with carpus and chela reaching beyond 

 antennal scale; fingers of chela somewhat longer 

 than palm; carpus as long as merus. Second legs 

 strong, unequal in size and shape; carpus and 

 chela reaching beyond antennal scale. On one leg, 

 fingers about half length of palm; immovable 

 finger somewhat higher than dactyl and bearing 

 two large teeth on cutting edge, anterior tooth 

 triangular, at middle of edge, posterior tooth 

 truncate with crenulate margin; dactyl with one 

 tooth; palm with upper and lower margin some- 

 what compressed, surface appearing minutely 

 roughened under magnification; carpus short, 

 conical, with a depression above and a knob below ; 

 merus a little longer than carpus. Other second 

 leg much as above but with relatively longer 

 fingers; immovable finger higher in comparison to 

 dactyl; teeth smaller and carpus more slender. 

 Remaining legs with bifurcate dactyls. 



Abdomen with first five pleura broadly rounded. 

 Sixth segment with pleura and posterolateral 

 angle ending in slender, sharp spines; slightly 

 lunger than fifth segment. Telson half again as 

 long as fifth segment ; two dorsal pairs of spines 

 on lateral margin of telson small, almost invisible; 

 anterior pair about in middle, posterior pair closer 

 to posterior border than to anterior pair; posterior 

 border with three pairs of spines in a row; inner 

 i wo pairs equal in length, outer pair smaller; 

 uropods broadly ovate, outer margin of exopod 

 ending in blunt angle with small movable spine 

 at tip. 



Measurements. — Length of body : male 32 mm. 



Color.- — Translucent white. 



Habitat. — The species lives commensally in 

 lamellibranch mollusks in coastal waters and has 

 been recorded from Atrina seminuda, A. serrata, 

 and Pecten sp. (Holthuis, 1951a) ; shallow water 

 to 23 fathoms. 



Type locality.- — South Carolina. 



Knoxon range. — Atlantic Beach near Beaufort 

 Inlet, N.C., to Chandeleur Islands, La.; Baha- 

 mas; Madeira. 



Remarks. — Brooks and Herrick (1892) illu- 

 strated a section through the segmenting egg of 

 Pontonia domestica on plate 28. 



Pontonia margarita Smith 



Figure 40 



Pontonia margarita Smith, 1869c, p. 245. — Holthuis, 1951a, p. 

 13X, pi. 43, figs, a-1 ; pi. 44, figs, a-h (rev.). 



Recognition characters. — Rostrum depressed 

 and decurved, dorsally flat and triangular; tip 

 reaching to end of basal article of antennular 

 peduncle or slightly beyond; an inconspicuous 

 dorsal and ventral tooth near tip with small tuft 

 of hairs between upper tooth and apex; a longi- 

 tudinal median carina ventrally. Carapace 

 smooth; with strong antennal spine located well 

 below narrowly rounded lower orbital angle; 

 anterolateral angle broadly rounded and ante- 

 riorly produced. Eyes somewhat larger than in 

 P. domestica. reaching laterally beyond antennal 

 spine. Basal article of antennular peduncle with 

 blunt-pointed stylocerite more or less pressed 

 against outer border; anterolateral angle of article 

 produced forward, rounded; upper antennular 

 flagellum short, thick, curved backward; fused 

 part with six or seven joints; short ramus with 

 two joints. Antennal scale with convex outer 

 margin ending in small inwardly curved distal 

 tooth, lamella far exceeding tooth. 



First leg with half or more than half of carpus 

 reaching beyond antennal scale; fingers longer 

 than palm, unarmed; carpus longer than merus. 

 Second legs unequal in size but similar in shape. 

 Larger leg with fingers a little over half length 

 of palm; palm twice as long as deep, somewhat 

 inflated; dactyl narrower than immovable finger 

 and bearing one large tooth slightly behind mid- 

 dle; cutting edge of immovable finger with two 

 large teeth fitting on each side of opposed dactylar 



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FISH AND WILDLIFE SERVICE 



