338 ON THE MUSCULAR AND ENDOSKELETAL SYSTEMS OF LIMULUS. 



last pair of branchio-thoracic muscles are seen, rising from the front edge of 



the metasomatic stemite (p.ab.st). 

 Fig. 3. Ventral view of the plastron or thoracic entochondiite, after all muscles have 



been removed. 

 Fig. 4. View of the dorsal face of the plastron, with the various plastro-tergal and 



plastro-entapophysial muscles &c. 

 Fig. 5. Dorsal view of the plastron, the left edge cut away to show the plastro-coxal 



muscles (32-44) entering the entocoxites. (The dorsal process (d.cen) is 



represented as rather too rounded at the top.) 

 Fig. 6. Ventral view of the plastron, with the various plastro-coxal muscles attached on 



the observer's right. 

 Fig. 7. An entocoxite, being the inner articular surface of a prosomatic appendage. 



It is made up of an anterior (ab) and a posterior (pb) border, and superiorly 



of a knob (k) to which the tergo-coxal (25) is attached, and of a coxal pivot 



(cp), by which the appendage is articulated with the sternal plate of the 



carapace. 

 Fig. 8. A mesosomatic entochondrite seen from below. 

 Fig. 9. A mesosomatic entochondrite from in front (represented with its ventral face 



upwards). 

 Fig. 10. A transverse section across the mesosoma (from C to D, PI. LXXII.), showing 



the thick wall, with a canal within it. The sternal region rises to meet 



the tergal, and leaves but a narrow membranous area for the attachment of 



the appendage (x), which has been removed. 

 Fig. 11. A transverse section across the metasoma (from A to B, PI. LXXII.), showing 



complete chitinous floor (p.ab.st). 



