PLATE IX. 



FIG. 16. Transverse section through a rather small Lepisosteus osseus taken 

 33 mm. behind the opercle as seen from the rear. Shows the main longitudinal 

 lymphatic trunks in section. Natural size. 



FIG. i6a. Transverse through the ventral lymphatic trunk region 20 mm. 

 caudad of Fig. 16 as seen from the rear. Natural size. 



FIG. i63. Transverse section through the ventral lymphatic trunk region 20 

 mm. cephalad of 16 as seen from the rear. Note the trunk is curving off to the 

 right preparatory to emptying into the right pericardial sinus. Natural size. 



FIG. 17. Represents the inner or posterior surface of the first branchial arch 

 of a yo-pound Polyodon. Except at the two extremities the gill rakers are cut at 

 their bases so as to best display the branching of the lymphatics (veins?) over 

 the surface of the arch. At one place a few of the inner branchial filaments are 

 removed to show the position of the branchial lymphatic trunk (nutrient 

 branchial vein ?) in relation to the afferent and efferent branchial trunks. Pre- 

 ceding this gap the filament lymphatic network (nutrient venous network ?) is 

 indicated on the outer surface of several of the filaments. X i* 



I 4 2 



