24 



PATTEN AND REDENBAUGH. 



fibers. Alongside the chilaria it is attached to the integument by a similar bundle 

 of connective tissue. 



Fig. 3. X zy^. Posterior portion of plastron of Limulus and first abdominal 

 endochondrite, with posterior half of oesophageal collar (pe. col.) and nerves, 

 neural side. Four of the cross-commissures (cr. com.) are shown. In each neu- 

 romere are two pairs of nerves — a neural pair {n. n.*^^) and a haemal pair {h. n.*-^). 

 Of the neural nerves, n. n.*, n. n.^, and n. nfi supply the fourth, fifth, and sixth 

 pairs of legs respectively ; n. «.^ the chilaria ; and n. ti.^, the operculum. All the 

 haemal nerves supply the skin of the carapace and other organs; h. n.'' and h. nP 

 give off small nerves {in. n.^ and in. nP) through the first and second pairs of 

 foramina (/.' andy.^) respectively; h. n? also gives off a small nerve (in. tt.^) just 

 posterior to the plastron. This is seen through the semi-transparent connective 

 tissue attached to the capsuliginous bars. These small nerves {in. n.^-^) com- 

 municate with the sympathetic system supplying the intestine and longitudinal 

 abdominal muscles. The nerves n. «.^~^ k. «.'-^ and the ventral cord {v. c.) pass 

 through the occipital ring. The ventral cord passes haemal to the abdominal 

 endochondrites, the first of which {ab. en.) lies at the base of the operculum. The 

 shallow pits {op. m.) on the surface of this endochondrite, similar to those on the 

 occipital ring, represent the attachments of a pair of muscles entering the opercu- 

 lum. Posterior and anterior to these pits the endochondrite is in contact with 

 the integument. In some cases the anterior and posterior processes {a. p. and/./.) 

 of successive endochondrites are continuous with each other as thin strands of 

 connective tissue. The haemal processes {h.p.) which straddle the ventral cord 

 give attachment to haemo-neural muscles. 



Fig. 4. X 2. Endosternite of Limulus from posterior side, showing the occi- 

 pital ring {oc. r.) and its relation to the nerves. The portion of the plastron 

 anterior to the occipital ring is not represented. 



6". is a thickened shoulder uniting the bases of the latero-posterior processes 

 {l.p.pr.). Other reference letters as in Fig. 3. 



