THE GENERA AND SPECIES OF SYM PHYLA. 91 



forms of this <>roap by the very thick plumose setse on 

 the aiitenua3, which, besides, typically possess a higher 

 number of joints than in any other species of the genus. In 

 the set^ on the posterior legs it agrees essentially with S. 

 vulgaris and allied forms, but it is widely separated from 

 them by the shape and clothing of the cerci. 



EXPLANATION OF PLATES 1—7, 



Illustrating Mr. H. J. Hansen's paper on " The Genera and 

 Species of the Order Symphyla." 



PLATE I. 



Fig. 1. — Scutigcrellu immaculata (Newp.), from Europe. 



Eig. la. — Appendages of the moutli, cleaned with caustic potash, from 

 below. X 61. The mandible on the right side of the fiL,'ure omitted. 

 a. Proximal joint of the mandible. 6. Basal part of a muscle to the proximal 

 joint, c. Distal joint of the mandible, d. Tendon to the distal joint. 

 e. Maxilla. ./. Maxillary palpus, t/. Sternum of the segment bearing the 

 labium, k. Basal joint of the labium, i. Second joint of the labium. 

 h. Two pairs of lobes on the labium. I. Lateral skeleton of the head. 



Fig. lb. — Distal joint of the right mandible, from above. X 160. 



Fig. 1 c. — A small part of the cutting edge of the same mandible with its 

 " lacinia mobilis," /. x 375. 



Fig. Id. — Inner chitinous plates,/;, of the head, the hypopharynx, /i, and 

 the maxillulse, m, seen from above. X 61. 



Fig. le. — The hypopharynx, k, and the maxillulcc, m, from above. X I'JO. 



Fig. ly. — The process containing the calicle with the tactile hair, seen from 

 the outer side. X 200. (. Basal part of the tactile hair. 



Fig. ly. — One of the seta3 from the margin of the calicle shown in Fig. 

 1/. X 400. 



Fig. 1 h. — The same calicle with the basal parts of the tactile seta. X 100. 



Fig. 1 i. — The twenty-fifth joint of an antenna with fifty joinis of a speci- 

 men from Rome, seen from the outer side. X 90. 



Fig. 1 k. — Second scutum of a large specimen from Rome. x 36, 



