CONUS ARTERIOSUS IN TARPON ATLANTICUS. 



149 



the proximal l and distal l rows appear to be approximately equal 

 in size, this however is far from being the case, those of the 

 distal row having a capacity far exceeding that of the proximal. 

 The proximal valves are extremely fleshy at their attached 

 margins, and shade rapidly into a thin semilunar area near 'the 

 free edge ; the edge itself is marked by a cord-like thickening, 

 and is quite unattached, except at either end, where, having 

 blended with the corresponding extremity of the other cusp, it is 

 attached dorsally and ventrally to the mid-line of the bulbus a 

 short distance beyond the conus. 



The distal valves are not so fleshy as the proximal, and the 

 marginal semilunar area is very thin and profusely perforated. 



The margins are free except 

 at their extremities, the dorsal 

 ends of the right and left valves 

 blend at the mid-longitudinal 

 region of the bulbus, and be- 

 come continuous with an elas- 

 tic cord, the other end of 

 which is attached to the dor- 

 sal bulbus wall at its distal 

 extremity. The ventral ex- 

 tremities of the distal valves 

 blend at their point of attach- 

 ment in the mid-line at the 

 junction of the proximal and 

 middle thirds of the ventral 

 bulbus wall. 



That the capacity of the dis- 

 tal valves is much greater than 

 that of the proximal, is shown 

 by the fact that a probe can 

 be passed 1 1 mm. into the 

 former, and only 3 mm. into 



the latter. To illustrate this point, a frontal section passing ap- 

 proximately through the mid -lateral line of another heart is 

 shown in Fig. 3. 



1 The terms proximal and distal are used with regard to the ventricle. 



FIG. 3. Ventral face of a frontal sec- 

 tion of the heart from the smaller, Tarpon 

 its approximate source is indicated by the 

 broken line in Fig. 3 ( X | ) &> lumen 

 of bulbus arteriosus ; C, conus arteriosus ; 

 D, cavity of right distal conus valve ; 

 P, cavity of left proximal conus valve ; V t 

 wall of ventricle. 



