SYMPHYLA 465 



Order 1. PROGONEATA. 



Body usually cylindrical; usually 2 pairs of legs to a segment; but 

 one pair of maxillae; with anteriorly placed genital pore; tracheae with- 

 out anastomoses and spiracles which cannot be closed: 3 suborders. 



Key to the suborders of Pro'goneata: 



Oi Animals minute ; but 1 pair of leg:s to a segment. 



6i Antennae not branched 1. Symphyla 



62 Antennae with 3 terminal branches 2. Pauropoda 



«2 Animals not minute ; 2 pairs of legs to most segments ; millipeds. 



3. DiPLOPODA 



Suborder 1. SYIVIPHYLA.* 



Minute, colorless myriapods with a flattened body consisting of a 

 head and 14 segments, with 12 pairs of legs, each of which terminates 

 with 2 claws; projecting from the basal joint of each leg of the 10 hinder 

 pairs is a minute movable branch or parapod; antennae long; eyes absent 

 or minute; mouth parts consist of a pair of mandibles and a pair of 

 maxillae which form a sort of underlip ; a pair of long thick cerci project 

 from the hinder end of the body, each of which has a spinning gland; 2 

 spiracles present at the base of the antennae; the median, genital pore is 

 in the fourth segment ; young born with 6 or 7 pairs of legs : 1 family, 2 

 genera, and about 24 species, of which 4 are American, which are active 

 animals, found under stones, etc., in moist places. 



Family SCOLOPENDRELLIDAE. 

 With the characters of the order: 2 genera. 



1. ScUTiGERELLA Ryder. Posterior margin of all the dorsal plates 

 except the last either convex or emarginate, with 2 lobes; head shai-ply 



separate from the trunk in the mid-dorsal area; first pair of legs well 

 developed and more than half as long as the following pair: 10 species, 

 2 in America. 



* See "The Structure, Affinities and Species of Scolopendrella," by ,T. A. Ryder, 

 Proc. Acad. Nat. Sci., Phila., for 1881, p. 79. "Scolopendrella and Its Position in 

 Nature," by A. S. Packard. Jr., Am. Nat., Vol. 15, p. 698, 1881. "The Genera and 

 Species of the Order Symphyla," by H. J. Hansen, Quart. Jour. Mic. Soc, 1903. 



