THE SPIDER CRABS OF AMERICA 145 



postorbital small, minute, or wanting. Basal article of antenna 

 triangular; movable part concealed beneath rostrum. Chelipeds of 

 male strong; fingers either gaping or in contact; tips excavate or 

 spoon-shaped. Ambulatory legs subcylindrical, diminishing suc- 

 cessively in length from first to fourth; propodites sometimes with an 

 inferior tooth or bunch of setae; dactyli with two rows of spinules 

 beneath. Abdomen of male with six or seven segments, of female 

 with five or seven segments. Small species. 



Found on both sides of the American continent, from southern 

 California to Chile and from northern Florida to the State of Santa 

 Catharina, Brazil. Bermudas (Verrill). South Africa (Stebbing) . 



The subdivision of the motley genus Epialtus was suggested by 

 A. Milne Edwards and by Miers.-^ The former went so far as to 

 make three subgeneric divisions which he formed on two characters, 

 the absence or presence of lobes on the rostrum and of a tooth on the 

 lower margin of the propodites of the legs. This grouping would 

 bring together species known to-da}^ which differ widely in other 

 respects and would separate other species which are in the main 

 closely related. It is possible, however, to regroup the species on 

 general characters. On this basis I have placed the three large oval 

 species of similar aspect, occurring on the west coast of America, 

 in the genus Taliepus (subgenera Nos. 2 and 3 of A. Milne Edwards, 

 exclusive of E. productus). E. productus is more closely related to 

 Pugettia than to true Epialtus and has been transferred to that 

 genus. 



This leaves in Epialtus numerous small forms which are wonder- 

 fully diversified, but indubitably of one genus. 



The species with bilobed rostrum appear to be derived from those 

 with simple rostrum, and those rostra which approach an oblong 

 shape are more likely to be divided than those which are triangular 

 or linear. E. dilatatus shows the simplest form of bilobed rostrum, 

 the lobes so shallow that Milne Edwards, while figuring the emargi- 

 nation, yet groups the species among those with entire and obtuse 

 rostra. The character of the propodal tooth may be the result of 

 environment, the habit of clinging to algae having perhaps required 

 a means of attachment afforded by subchelate ambulatories. At 

 present we know too little of the relative habits of E. bituberculatus 

 and E. hrasiliensis to determine why, with similar carapaces and 

 chelipeds, one should have slender, unarmed propodites and the 

 other, stout propodites provided with a strong, digital tooth. 



Various forms allied to hituberculatus have been described in the 

 past but their relative value has been in doubt owing to intermediates. 

 In recent years the collection in the National Museum has increased 

 to such an extent that it is possible to say, with a fau- degree of 



*' Journ. Linn. Soc. London, vol. 14, 1879, p. 650. 



