FISHERY BULLETIN: VOL. 72, NO. 1 



range, platychela being intermediate and plnnia- 

 ta occupj'ing the low end. Females follow the 

 same general i)attern, but iiiorii and sob7i)ia 

 show considerably less overlap. . 



Length of Furcal Rami 



The length of both rami is directly related to 

 prosome length as well as TL. Shortening and 

 fusion of the right ramus in adult females in- 

 troduces asymmetry but the change does not 

 alter the essential relationship to body length. 

 Ill the female sex (Figure 25) niorii and sobrnua 

 occupy one side of the overall distribution of 

 length of the right ramus, platychela and 

 plumata the other with virtually no overlap 

 between the two pairs of species. Males show 

 more scatter (Figure 26) and apparent differ- 

 ences in allometry; sohrina and niorii tend to 

 diverge with respect to furcal length while 

 plumata and platychela tend to diverge with 

 respect to prosome length. 



Examination of furcal length relative to 

 furcal width increases separation of the three 

 equatorial species. It also enhances separation 

 of platychela and the Atlantic samples of plu ma- 



cr^ N = 49 

 platychela 



% N = 30 



o 



ID 



o 



UJ 



CE 25% 



25% 



25% 



25% 



plumata 

 2 N=75 



cr^N=50 

 morii 



% N = 35 



O^N = 5l 

 sobrina 



% N = 33 



2 8 I 3.0 I 32 I 3,4 1 3,6 I 3,8 I 4 I 



Prosome 

 Urosome 



Figure 24. — Frequency distribution of P:U ratio for both 

 sexes of the four species of Ponwllina. 



08 10 12 14 16 



LENGTH OF RIGHT FURCAL RAMUS, mm 



Figure 25. — Length of P (ordinate) plotted against length 

 of right furcal ramus (abscissa) for females of the four 

 species of Ponicllina. 



ta as well as separation of morii and the Indo- 

 Pacific samples of plumata (Figure 27). A 

 generally similar pattern is seen in the males 

 (Figure 28) except that morii and sobrina over- 

 lap freely with respect to the furcal length: 

 width ratio. 



ThIV-V Posterior Spine 



Strong sexual dimorphism appears in adults. 

 Among the females, plum,ata is unique; the base 

 of the posteriorly directed spine rises roughly 

 at the level of the proximal margin of the genital 

 segment, the spine is robust and broadly trian- 

 gular in both dorsal and lateral views (Figure 

 3a, d-f). The spines in the three equatorial 

 species are similar to each other in being dimin- 

 utive and needlelike or dentiform. They differ 

 primarily with respect to relative length of 

 the spine (Figures 6a, c, g, h; 9a, c, e, f; 11; 13a, 

 c, g). 



The ThIV-V spine in males appears in three 

 states: plumata exhibits a minute denticle that 



96 



