212 



TTIE MYRTARODA OP NORTH AMERICA. 



S. ANNULATUS. 



" Body with numerous, elevated, obtuse lines, of which four arc above the stigmata ; 

 ultimate segment glabrous, unarmed." 



" Body cylindrical, emarginate, above brownish with a slight tint of red, immaculate, 

 beneath yellowish white ; segments each with about fifteen elevated obtuse lines, of which 

 four are equal dorsal, a pyriform larger oblique one on the stigmata, and about ten 

 decreasing in size to the feet, anterior segment as long as the three succeeding ones con- 

 junctly and glabrous, posterior one glabrous reddish brown, as long as the two preceding 

 ones, united and obtusely rounded at tip; head whitish before; antennas white ; eyes 

 transverse linear, black ; vertex not distinctly impressed." 



I. annulatus, Say, Journ. A. N. S., 1st scries, vol. ii, p. 103. 

 S. annulatus, Newport. 



Species mihi ignota. 



Fam. POLYDKSMIDyK. 



Stoma ot scuta arcto conjuncta; scuta laminis lateralibus instructa. 



Sterna and scuta .closely cemented together; scuta furnished with lateral lamina. (Fig. 40.) 



• 



The head in the Polydcsmida? is large and massive. The absence of eyes and the small 



antcnnsc point to a state of low development of the special 

 sinses. The female genitalia are placed in the third seg- 

 ment, just posterior to the second pair of legs. They are 

 generally more or less hidden within the body. The male 

 organs are situated in the seventh segment, replacing the 

 eighth pair of legs. They generally project from the body so 

 as to be very prominent. 



Authors generally have divided this family into genera, 

 founded upon the size and form of the lateral lamina. But, as II. l)e Saussure (he. cit.) 

 has remarked, these characters are relative, and the differences so merge into one another 

 that the groups cannot be well defined or separated by distinct border lines. He there- 

 fore has very properly adopted these groups as subgenera. Fontaria, he thinks, has more 

 claims as a distinct genus than the others, but even this is scarcely worthy of the higher 

 rank. He takes for his generic characters the position and numbers of the lateral pores. 

 In this I have followed without feeling sure but that at some future time still better cha- 

 racters will be elucidated. Two forms herein described apparently do not belong in the 



