644 PROCEEDESTGS OF THE NATIONAL MUSEUM vol. iis 



gonopocls broadly sickle shaped, rather than obliquely T-shaped 

 (see fig. llh). 



The genus Pachygrapsus is in need of intensive study and possible 

 revision. As a contribution toward such a review, illustrations are 

 ofi'ered in figure 11 of the gonopods of the described species in the 

 national collections. Whenever possible, topotypic males have been 

 selected. This study has demonstrated the importance of the gono- 

 pods at the species level in this genus. It has confirmed that Sesarma 

 murrayi Caiman, 1909, is identical with Pachygrapsus minutus A. 

 Milne-Edwards, 1873 (see Schmitt, 1939, p. 22) and that P. longipes 

 Rathbun, 1893, is a synonym of P. planifrons De Man, 1888 (see 

 Edmondson, 1959, p. 175); the latter species seems to attain a some- 

 what larger size in Hawaiian waters than it does in Indonesia, but 

 the gonopods are identical. How important the gonopods are at the 

 generic level remains to be demonstrated. Those examined fall into 

 two categories. One group [P. crassipes Randall, 1839; P. gracilis 

 (De Saussure, 1858); P. marmoratus (Fabricius, 1787); P. maurus 

 (Lucas, 1849); and P. minutus] has a dense brush of stout, amber 

 setae which completely conceals the tip of the appendage. The other 

 group [P. loveridgei; P. planifrons; P. plicatus (H. Milne Edwards, 

 1837); and P. transversus] bears more slender, longer setae which do 

 not cover the chitinous end-piece. Attempts to relate these differ- 

 ences to other morphological characters have not been entirely suc- 

 cessful. A cursory examination of the species available to me, how- 

 ever, shows a possible correlation between the two groups of species 

 and the presence or absence of the conspicuous, but delicate, brush 

 of plumose setae on the anterior surface of the first pah' of walking 

 legs. Such a brush was found in P. loveridgei, P. minutus, P. plicatus, 

 and P. transversus. Although P. minutus is placed in the first group 

 of species above (which otherwise lack plumose setae on the first 

 walking legs), it might be assigned to either group; the endpiece of 

 the gonopod is hidden by a few stout setae, but it does not project 

 at an angle to the axis of the appendage as it does in the other species 

 of that group. Also, the brush of setae was not observed in any of 

 the available specimens of P. planifrons, a species that seems to 

 belong to the second group on the basis of its gonopod. These setae 

 are frequently lost in museum specimens, however; it would be im- 

 portant to know if they are present in fresh material of this species. 

 A detailed study of the gonopods of all species of the family Grapsidae 

 might yield worthwhile information on generic relationships. 



Distribution : P. loveridgei is known only from St. Helena. It will 

 be noticed that 85 of the 211 specimens were found on the buoy 

 alone and were therefore living at or near the surface; it is not known 



