150 PATTEN AND REDENBAUGH. [Vol. XVI. 



In the fourth and fifth appendages the ento-coxal nerves are 

 essentially the same as in the third appendage. 



In the sixth appendage (Text-fig. 12 ; PI. VII, Fig, 2) there is 

 an interesting variation. The anterior and posterior ento-coxal 

 nerves (a.e.n. diwd p.e.n.) are similar to those in the third append- 

 age, except that they arise at some distance from the brain ; but 

 the median ento-coxal nerve {nt.e.n.) is much enlarged and be- 

 comes the flabellar nerve, which breaks up into many filaments 

 inside the flabellum {flab.) and supplies the numerous sense 

 buds of this organ. It also gives off a few branches to the 

 epidermis around the base of the flabellum. A large blood 

 vessel accompanies it into the flabellum. 



(c) Pedal Branches. (See Text-fig. 11). — In the coxopodite 

 {\-cox) the main pedal nerve gives small branches to the flexor 

 (/^) and extensor muscles {e.^) of the basipodite {2-bas.). A 

 larger branch, the external pedal nerve {e.p.n.), leaves the 

 outer side of the pedal nerve and runs parallel to it along 

 the outer side of the leg, through all the joints as far as 

 the distal end of the propodite {5-pro.). This branch is found 

 in all the thoracic appendages, not excepting the chelicerae, 

 and seems to be mainly sensory in function, though it does 

 supply a few muscles. 



The main pedal branch, or internal pedal nerve {i.p.n.), lies 

 for the most part toward the inner side of the leg between 

 the muscles of the anterior and those of the posterior sides. It 

 gives off both sensory and motor branches all along its course, 

 and supplies all the muscles not supplied by the external pedal 

 nerve. In the second, third, fourth, and fifth legs it terminates 

 in four branches, two to each blade of the chelae. 



In the propodite of the sixth leg (Text-fig. 12) it gives off 

 numerous branches to the spatulate organs. The main branch 

 continues into the slender outer joint (p-ciac), and, after sup- 

 plying the extensor and flexor muscles {e.7 and/". 7) of the termi- 

 nal chelate portions, divides into two branches which distribute 

 themselves in the two terminal joints. 



(2) Haemal Nerves. — The typical haemal nerve (Text -fig. 8) 

 consists of three branches, an intestinal {i.n.), a cardiac (s.c.n.), 

 and an integumentary branch (in.n.). In most of the thoracic 



