ASTACID^E. 57 



II. GROUP. (Type, C. affinis.) 



The third legs of the males hooked ; rostrum subquadrangidarly elongated, 

 with an anteapical tooth on each side, at least in the young ; first pair of abdom- 

 inccl legs bifid, elongated, straight and acute at the tip. 



This group seems very natural, if we except two abnormal species, 

 C. immunis and C. extraneus. C. lancifer is to be considered in some de- 

 gree as an exaggerated form of this group. 



Well-developed hooks always appear on the third pair of legs of the 

 male ; on the fourth pair they are never to be found ; in very rare 

 instances the second pair shows similar incipient hooks more largely de- 

 veloped (as in C. virilis). 



The rostrum is exceedingly long, more than three times longer than 

 broad, in C. lancifer. In all the other species the rostrum is twice, or 

 less than twice as long as broad, of a more subquadrangular form ; ex- 

 cavated, the margins thickened and parallel ( 0. affinis), or concave on 

 the sides ( 0. juvenilis and C. placidus), or flattened, more or less straight 

 on the sides, in the other species. The apical tooth and the two la- 

 teral teeth are all well developed, at least in the young. In C. immunis 

 alone the shape of the rostrum is very different in the full-grown 

 species. The rostrum is conical, short, and toothless, as in the third 

 group ( C. Bartonii) ; nevertheless, according to the form of the abdom- 

 inal legs, it belongs to the group of C. affinis. 



The foreborder of the cephalothorax is strongly angulated behind the 

 antennas in C. lancifer, C. extraneus, C. immunis, and C. affinis, straight or 

 slightly notched in all the other species. This character serves to sep- 

 arate the species otherwise related to C. affinis into two sections of equal 

 value. 



The first pair of abdominal legs is always strongly bifid, the tips 

 much elongated and acute. In C. lancifer, while the tips are not so 

 much elongated, they are somewhat flattened, but apparently of the 

 shape characteristic of this group. A remarkable exception is to be 

 found in C. extraneus, which has the first pair of abdominal legs of the 

 shape peculiar to the third group ( C. Bartonii) ; but the rostrum and 

 other characters prevent me from placing them otherwise than in the 

 group of C. affinis. 



The body and the hands in the species of the second group are shorter 

 and broader, except in C. lancifer, which more nearly resembles the spe- 

 cies of the first group. The flagellum of the inner antennas has the in- 

 ternal branch visibly narrower, and sometimes even a little shorter, 

 than the external branch. The lamina of the antennas is smaller, 

 shorter, and dilated in the middle, except in C. lancifer, the lamina of 

 which has exactly the form described in the first group. The epistoma 



