16 PROCEEDINGS OF THE NATIONAL MUSEUM V0L * 124 



(mean NFD 7.2, TD 2.5), the two species of Arenaeus scarcely can be 

 excluded from this assemblage; thus, A. cribrarius % is closer to C. bel- 

 licosus @ (NFD 11) than this species is to C. exasperatus @, C. gladi- 

 ator %, and C. marginatus @. It would seem desirable to re-examine 

 these genera in the first instance by a detailed classical approach. (5) 

 The genus Portunus covers a wide range of morphological diversity. 

 If only the P. pelagicus group and the P. xantusii group are considered, 

 clearly these should belong to different genera. 



Inspection of the models: On the one hand, this confirmed visually 

 the main conclusions (1), (2), (4), and (5) above; on the other hand, 

 the validity of separating Scylla from the P. pelagicus group appears 

 very doubtful. In addition, the detailed relationships of individual 

 species are altered; for example, P. sayi @ becomes the closest species 

 of the P. pelagicus group to Callinectes; also the closest approach of 

 Arenaeus and Callinectes species are A. mexicanus © and C. marginatus ©. 



Evidences of parallel evolution within the genus Portunus. — 

 The following main groups have been recognized in the above discus- 

 sion: (1) 15 species group centered on P. xantusii) (2) P. pelagicus 

 group; (3) P. longispinosus group, represented in America by P. tuber- 

 culatus @>; (4) P. vocans group, containing a second species from the 

 Indo-West Pacific; (5) an indistinct P. bahamensis group, containing 

 P. bahamensis @, P. depressifrons (13), P. anceps ©, and P. floridanus 



<g>. 



In many cases a given taxonomic feature occurs in species belonging 

 to two or more of the above groups. In a few cases it occurs in only 

 some of the species of the groups, in which case presumably parallel 

 evolution has occurred. Excluding secondary sexual characters of the 

 males, the features showing parallel evolution are as follows (feature 

 numbers are from table 1, unnecessary negatives having been elimi- 

 nated) : 

 2 Median frontal lobes forming pointed teeth. 



6 Inner supraorbital sinus open. 



7 Third maxilliped not conspicuously hairy. 



11 Carapace not hairy. 



12 Carapace broad. 



14 Postlateral junction of carapace spinous. 



16 Mesogastric area of carapace with broad granular ridge. 



26 First anterolateraktooth more slender than second. 



28 Last anterolateral tooth distinctly long. 



29 Chelae attenuated. 



SO Chelae robust. ■■ 



31 Undersurface of chelae with squamiform markings. 



33 Posterior border of arm without spines. 



37 Hand of chelae swollen. 



39 Upper surface of hand with single spine. 



40 Posterodistal border of merus of fifth leg spinulose. 

 57 Iridescence present somewhere on body. 



