NO. lO I'KEUlNt; UKCiANS OF AK'Al. U N lUA — SNOlXiRASS 



Fig. 2. — Cephalic structures of Arachnida, Xiphosurida, and an anii)hipod 



crustacean. 



A, anterior view of an arachnid, diagrammatic, tlie under lip represented as 

 the pedipalp sternum (IIS) as in Araneida. B. the same with chelicerac removed 

 and the mouth parts sectioned transvirsely behind the palps, exixisiuR the pliarynx 

 and its muscles. C, IJmulus polyphcmus L., the mouth region, anterior, with 

 right chcliccra and base of riplit pedipalp. I), diagrammatic longitiHlinal section 

 oi A, showing the prcoral cavity {PrC), pharynx (P/iy), and dorsal pharyngeal 

 muscles (did) arising on the epistome (Epst). K, Talorchcsiia lofujiconus Say, 

 amphipod crustacean, anterior view of head showing second antennae (J.tnt) 

 in jKDsition of cheliccrae ni an arachnid (A. Chi)- I"". Trochosa embr)-o, longi- 

 tudinal section of anterior end. showing jKisition of frontal ganglion (frO) 

 (from Holmgren, 1920, somewhat simplified). 



