38 



ON THE CHILOPODA OF NORTH AMERICA. 



many contortions. On examining it, we found that it contained the derm of the head 

 and all its appendages, even to the maxillas and maxillary palpi. The anterior por- 

 tion of the skin was so torn as to show that the process of shedding probably com- 

 menced by the creature's withdrawing its head from its case, and then thrusting it 

 out between some of the anterior sterna, completing the process by pushing the skin 

 back with its legs aiding them by a peculiar wriggling motion. The exuvia has most 

 of the posterior segments entire, showing that the occupant has been withdrawn from 

 it like a hand from a glove. The animal is of a milk-white color, with the antennas 

 pubescent, and the lateral anal appendages not elongate and without spines. The 

 lower spine on basal joint of last pair of legs is very small, and the upper one scarcely 

 perceptible. We once had the pleasure of observing a female guarding the young. 

 Being on her side, with her body coiled around them, she, by a rapid, cilia-like action 

 of her feet, would pass them along and arrange them to suit her. This species is 

 one of the most common chilopods around Philadelphia. The southern specimens 

 are much larger, stouter and more highly colored than those from colder regions. 



Specimens belonging to the Smithsonian Institution. 



S. GRACILIS, n. sp. — S. ferruginea ; capite labioque leviter punetato, segmento-cephalieo subovato ; antennis 

 pubescentibus ; labii margine antico modiee angusto, lateribus obliquis apice emarginato et angulis aeutis ; 

 pedibus flavis subcompressis ; scutis sternisque vis punctatis; pedibus postremis gracillibus, elongatis, 

 singula spinis duobus S. sexspinosa: illis simillimis, articulo basali tibiali longiore, articulis tribus ultimis 

 pubescentibus ; appendicibus analibus lateralibus elongatis, rude punctatis, singula spina apicali unica 

 (iuterdum bifida) alteraque minutissima in augulo superiore posteriore ; squama prcanali elongata, punc- 

 tata, postico late emarginata. 



Color in all of our specimens lighter and more ferruginous- than the typical color of 

 S. sexspinosa, but further investigations may show that that of this form also darkens 

 with age. Prebasilar fold generally well marked. Scuto-episcutal sutures distinct; 

 sterno-episternal absent, but a suture marking the line of coalescence of the primitive 

 sterna is often very apparent. This species is closely allied to the preceding as well 

 as to the following. It differs from both in the shape of the anterior margin of the 

 labium, in the scarcity of punctations on the body, and in the pubescence of distal 

 portion of the last pair of feet. The superior spine of the lateral anal appendages is 

 perhaps a little larger than in S. sexspinosa, but certainly smaller than in S. spinicauda. 

 The white blotches beneath the posterior feet are common to all the North American 

 species. 



