346 



poi'tance. I refer for example to the separation of his subfam- 

 ily Ni>f(isj>iiliiui' from the subfamilies DanKfinif and Xoflin'iKc, 

 based upon the absence or presence of the lamell*. While the 

 lamellte are sometimes very constant in their shape and size in 

 a single species, yet, taking all the species together, we can get 

 an insensible gradation from forms with enormous shelf-like 

 expansions, wdiich conceal much or most of the cephalothorax 

 from above, to small chitinous ridges or only wrinkles of the 

 integument which may vary in some cases so as to be almost 

 invisible. This fact, taken together with the fact that there 

 are few if any supplementary characters in support of 

 this division, make it rather artificial, if not unwarrantable, 

 to accord it the same rank with his other divisions of 

 the group. On the other hand, his separation of those forms 

 which have the cephalothorax anchylosed to the abdomen 

 from those which have the cephalothorax hinged to the same 

 (his Plitliiracarhui') is certainly based on characters of family 

 portance. This is more convincingly evident when we con- 

 sider the other important points of difference, which are given 

 below'. 



Fiirins loltli Cephalothorax An- 

 chylosed to Abdomen. 



Body frequently depressed. 



With tracheae 



Ventral plate anchylosed to 

 dorsal plate 



Genital and anal openings sit- 

 uated apart. 



Legs frequently long or slender 

 or inoniliforni. 



Mouth-parts very small, or 

 rudimentary. 



Palpi with five segments. 



Femora generally stouter than 

 the other segments of the legs. 



Oephalotiiorax never with a 

 median rarina. 



Forms with L'ephalothoraiv 

 Hinged to Abdomen. 



Body always compresed. 



Without traclie;f. 



Ventral plate not anchylosed 

 to dorsal plate. 



Genital and anal openings us- 

 ually together 



Legs always stout. 



Mouth-parts large, mandibles 

 enormous. 



I'alpi with only four segments. 



Femora subequal in width to the 

 other segments of the legs. 



Cephalothorax often with a 

 median carina. 



