338 ON THE MUSCULAR AND BNDOSKELBTAL SYSTEMS OF LIMULUS. 



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



the metasomatic sternite {p.ah.st). 

 Fig. 3. Ventral view of the plastron or thoracic entochondrite, 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.c.en) 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 mthin 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. LXXIL), showing 



complete chitinous floor (p.ab.sf). 



