60 



transverse furrows. This last character is probably 

 not a permanent one. 



But the most distinguishing character, is the pro- 

 longation of the costal arches, particularly those of 

 the tail, beyond the membrane which they are sup- 

 posed to support; the termination of these arches is 

 in teeth or spines. Some species of the Asaph have 

 prolongated extremities to the ribs of the abdomen, 

 but we have never seen them on the arches of the tail* 



This genus is said to comprise a great number of 

 species, but the only one found in North America, as 

 far as our knowledge extends, is that described by 

 J. J. Bigsby, in the fourth volume of the Journal of 

 the Academy of Natural Sciences of Philadelphia. 

 As we have not seen the specimen, we add the de- 

 scription of it in the author's own words. 



PARADOXIDES BOLTONI. Bigsby. Figure 5. 



Oval, blind; surface with small tubercles and 

 striae; clypeus rounded before; exterior angle ex- 

 tending in a broad spine; abdomen fourteen jointed; 

 segments recurved, falcate; tail membranaceous and 

 serrate. 



The shape of this individual is oval, approaching 

 ovate; it is moderately flat; the whole length is five 

 inches and four-fifths; its breadth across the middle 

 is four inches and nine-tenths; wherever the cutis is 

 not removed, it is covered profusely and irregularly 

 with small tubercles. The denuded portions in this 

 specimen, for the space of three quarters of an inch 



