:io. 1659. AMERTCW FIPECTEf^ OF FiyyALPHEUSf—COUTIERE. 5 



lateral teeth, the ventral hook of the dactyls is almost as strong 

 as the dorsal, and the telson is straii>ht alon*? its posterior margin — 

 all characters not unusual in ISi/nalphcus. The other groups of 

 species vary more or less from the preceding; the nearest are the 

 pAixsoNi and Bkevicakpis groups, in which the stylocerite still 

 remains more prominent than the external spine of the basicerite, 

 and the antennal scale is never wanting and sometimes is very wide. 



The external spine of the basicerite begins to predominate in the 

 Neomeris group, but this group presents, besides, two characters of 

 the Hippolytida3 but little modified, viz, the movable spines often 

 present on the third and fourth meropodites and the frequent triun- 

 guiculation of the dactyls of the same feet, which is a vestige of the 

 series of spines present on the dactyl in many of the Eucyphota. 



There are no more than two hooks on the short and stocky dactyl 

 in the Biunguiculatus group, of w hich the ventral, the more feeble, 

 has a tendency to become normal to the lower border of the dactyl. 

 On the other hand, the shortening of the stylocerite and of the anten- 

 nal scale becomes very noticeable and the finger of the small chela of 

 the second pair carries a brush of hairs arranged in series. The 

 species grouped under this head are few, but they show the very grad- 

 ual connection between those Avhich precede and the L^evimanus 

 groujD, the most highly differentiated of the Synalpheids in the di- 

 rection of the " Reptantia." Here the antennal scale has very often 

 disappearecl without leaving any trace, the lateral spine of the basi- 

 cerite possesses a bulk wdiich contrasts with the slight importance of 

 the stylocerite, and the sexual differences often become very strong, 

 one might say exaggerated, in regard to the size of the abdomen of 

 the female and of the large cheliped of the male; finally, the finger of 

 the small cheliped, in which the carpus has, however, remained more 

 elongated than in any other grouj^, bears a curious structure com- 

 posed of from fifteen to twenty transverse row^s of long stiff hairs, 

 which are normal to the dactyl, and which diminishes in length from 

 behind forward ; this brush may be a cleansing organ in connection 

 with the very sedentary life of these species, or it may conceal from 

 the prey the extremity of the real prehensile chela. The only compar- 

 able organ in the Alpheida? is the tuft of long plumose hairs which is 

 borne by the chela of the second pair in Cheirothrix paruimanus Bate, 

 a genus, moreover, very like Synalpheus. 



