3*4 



ENDOCRANIUM, BRANCHIAL AND NEURAL CARTILAGES. 



The haemal ridges are split up into five pairs of haemal processes, h.pr. 1 5 , of 

 unequal length. The endocranium ends posteriorly in a short median process. 

 From nearly the whole of the neural surface muscles go to the base of the legs. 

 Haemo-neural muscles are attached to the haemal processes, and longitudinal 

 muscles to the posterior process. 



The oesophagus passes through the brain, between the anterior cornua, 

 to the sucking stomach which lies in the groove on the haemal side of the endocra- 

 nium. Muscle strands run from the stomach to the walls of the groove. 



Endocranium of Limulus (Figs. 2, 70, 75, 78, 209, 214, 215). The endo- 

 cranium of Limulus is the largest of any living arachnid. It is a rectangular 



I C 



T y 



ppr. Wj 



FIG. 213. Endocranium of Mygale. A, Neural surface; B, hasmal_* surface. Xs. After Patten and 



Redenbaugh. 



plate of nbro-cartilage, about three inches long, two and one-half inches wide, 

 and from one-eighth to one-half an inch thick on the margins. It lies near the 

 center of the cephalo thorax, with its anterior margin about opposite the cheli- 

 cerae, and its posterior one opposite the chilaria. It serves as a center of attach- 

 ment for the more important muscles of the thorax. The mouth is located a 

 little anterior to the center of the endocranium. From it the oesophagus passes 

 forward, through the brain, and between the anterior cornua to the mesenteron. 

 (Figs. 78-209.) The latter begins a short distance in front of the endocranium 

 and extends straight backward close to its haemal side. 



The neural surface of the endocranium is nearly flat and bounded on either 

 side by a sharp ridge or lateral wall. The anterior ends of the wall are much 

 higher and generally slope inward. (Fig. 215, A.) The posterior ends also in- 

 crease in height, turn inward and become continuous with the plate of cartilage 

 that forms the roof of the occipital region. The endocranium thus forms a shal- 

 low box, with low vertical walls along the sides and along a part of its posterior 

 end. There is no transverse anterior wall and no covering, or roof, except at the 



