Pre X r/ VA'I 



Fig. 17. — Head or head region of various arthropods. 



A. head and anterior body region of Eubranchipus vernalis (Phyllopoda, 

 Anostraca), with gnathal segments (/F, V, VI) distinct from protocephalon. 

 B, protocephalic head piece of Spironfocaris polaris (Decapoda) separated from 

 the carapace. C, carapace of Spironfocaris polaris from which the proto- 

 cephalon (B) has been detached. D, head and head carapace of Apus louf/i- 

 candata (Phyllopoda, Concostraca ) , dorsal view, showing segments IV , V , VI 

 added to protocephalon {Pre) and forming carapace. E, ventral view of 

 .same. F, head of PorcclUo (Isopoda) with maxillae removed. G, head of 

 Scntiqcra forceps (Chilopoda). H, head of Orchcstoidea calif ornica (Amphip- 

 oda)." I, head of Machilis (apterygote insect). J, cephalothorax and anterior 

 alxiominal segments of a scorpion (Arachnida). K, head of Eurynrus cryfhro- 

 pygus ( Diplopoda ) . 



a, dorsal (or posterior) articulation of mandible; Ant. antenna; lAiit, first 

 antenna; ^Ant, second antenna; c, anterior articulation of mandible; Ch, 

 chelicera; Cp, carapace; Cth, cephalothorax ; E, compound eye; Gch. gnatho- 

 chilarium; II', mandibular segment; iL, first leg; Lm, labrum; Md. mandible; 

 tMx. first maxilla; jM.v, second maxilla; iMxp, first maxilliped ; MxPlp, 

 maxillary palpus; Pdp. pedipalp ; Pre. protocephalon; iT , first tcrgum ; V, first 

 maxillary segment; /7, second maxillary segment; x, suture between proto- 

 cephalon and mandibular segment; y, suture between mandibular and first 

 maxillary segments. 



3 31 



