17 



the premaxillary nerve which the antecedent one (n 8) bears to the mandibvilar nerve, 

 and hokls the same relation in its coui'se to the apodemes iv & v. It forms the plexus 

 beneath that of the optic nerve, beyond which the filaments are lost in the tissues there. 

 The optic nerve crosses dorsad of the first four epimeral nerves in its course to the 

 compound eye. 



Fostmaxillary Nerve. — The fifth limb-nerve {n vi, Pis. II a. & IV.), with a more pos- 

 terior origin and a course more obliquely backward, repeats in limb vi — the homologue 

 of the postmaxilla, or second maxilla, in higher Crustaceans — the characters of the 'pre- 

 maxiUary nerve ' in relation to limb v. 



Sixth Epimeral Nerve [u 10, PL V.). — This repeats the same relative position of 

 origin to its answering limb-nerve as does n ^ ; it is continued further obliquely back- 

 ward before bending outward to its interapodemal space, and bifurcates before entering 

 there, the hinder division descending to supply the strong adductor muscle of the sixth 

 limb (vii in Pis. II a. & IV.). 



Maxilliiiedal Nerve (n vii. Pis. II A. & IV.). — The nerve supplying that limb has 

 its origin between the postmasillary nerve and the beginning of the abdominal gan- 

 glionic chord y. It repeats the character of the antecedent limb-nerves in relation 

 to its own articulated appendage, which is the homologue of tlie ' maxilliped ' in higher 

 Ci'ustaceans. 



Palpal Nerves. — At the interspace between the origins of the postmaxillary and maxii- 

 lipedal nerves, as in that between the latter and the ganglionic continuation of the neural 

 centre, arise filaments which supply the spinigerous process or ' palp ' of the compressed 

 denticulate haunch -joint (PI. II a. figs. 2 & 5, p). 



Chilarian Nerve (Pis. II a. n x, & IV. n*). This rises between the origins of ?i vii 

 & n VIII ; it is appropriated to and richly ramified in the leaf -like spinigerous appen- 

 dage, articulated behind the base of the maxiUiped, and closing posteriorly the circumoral 

 armatm-e. The serial homology of the chilarian with the palpal nervules lends some 

 countenance to that of the appendage, so supplied, being a detached spinigerous process 

 or ' palpus ' of vii. 



Seventh Epimeral Nerve (n 11, PL V.). — This arises dorsad of the origin of the max- 

 illepedal nerve, passes backward and outward to its proper apodeme (vi), where it 

 divides, and, running onward, ramifies to supply the tissues in the hinder produced angles 

 of the cephaletron. 



Eighth Epimeral Nerve {n 12, PL V.). — This is one of the same system of dorsal nerves, 

 succeeding the seventh ; it passes backward and slightly outward along the dorsal margin 

 of the seventh apodeme (vii), and dips into the articular depression between the cephal- 

 etron and thoi^acetron. 



Ojjercidar Nerve. — The hindmost pair of cephaletral ventral nerves {n, PL II a. & 

 n viii, PL IV.) is given off at or just before f the continuation of the neural ring into 

 the ' ganglionic chord.' The nerves of this pair run along the sides of the latter for 

 about 8 lines, then slightly diverge, curve outward, and send oil one or two filaments 

 laterally, before descending to penetrate the base of the anterior or opercular leaf-foot, 



t This lends countenance to the idea that the ' opercular liinh,' viii, is the last of the cephaletral series. 



D 



