194 BRITISH FOSSIL CRUSTACEA. 



the second, comes off behind it, from the lateral part of the ring, )3, and supplies the 

 limb homologous with the ' mandible ' (so called) in higher Crustaceans ; which limb is 

 marked iv in Pis. XXXIV and XXXV, where the nerve is traced through the coxal and 

 basal joints. 



" Fourth Epimeral Nerve. — Prom the dorsal aspect of the corresponding part of the 

 neural ring is sent off the ' fourth epimeral nerve ' (n, 8, PI. XXXVI), having the same 

 course and apodemal relations as the second and third of this series. 



"Premaxillary Nerve. — This, with a more posterior origin than the mandibular nerve, 

 repeats the characters of that nerve, in relation to the fourth limb, or homologue of the 

 ' praemaxilla,' or first or anterior maxilla, in higher Crustaceans. The nerve (n, v) is 

 shown in Pis. XXXIV and XXXV, entering and traversing the ' coxa ' and ' basis ' of 

 the limb marked v. This limb is sexually modified in the male of Limulus Molhccanus, 

 but not in the species here dissected. 



"Fifth Epimeral Nerve (n, 9, PI. XXXVI). — This repeats the relative position of 

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

 nerve, and holds the same relation in its course to the apodemes iv and 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. 



" Post-maxillary Nerve. — The fifth limb-nerve (n, vi, Pis. XXXIV and XXXV), with 

 a more posterior origin and a course more obliquely backward, repeats in limb vi the 

 homologue of the post-maxilla or second maxilla, in higher Crustaceans the characters of 

 the ' premaxillary nerve ' in relation to limb v. 



"Sixth Epimeral Nerve (n, 10, PI. XXXVI). — This repeats the same relative 

 position of origin to its answering limb-nerve as does n, 9 ; it is continued further 

 obliquely backward 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 (vn in Pis. XXXIV and XXXV). 



" Maxillipedal Nerve (», vn, Pis. XXXIV and XXXV). — The nerve supplying that 

 limb has its origin between the post-maxillary nerve and the beginning of the abdominal 

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

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

 Crustaceans. 



" Palpal Nerves. — At the interspace between the origins of the post-maxillary and 

 maxillipedal 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. XXXIV, figs. 2 and 5, p). 



" Chilarian Nerve (PI. XXXIV, fig. 1, n*, and PI. XXXV, fig. 1, »*).— This rises 

 between the origins of n, vn and n, viii ; it is appropriated to and richly ramified in the 

 leaflike spinigerous appendage, articulated behind the base of the maxilliped, and 



