CONUS ARTERIOSUS OF MEGALOPS CYPRINOIDES. 379 



measurement the two halves were imbedded in celloidin and cut 

 into serial sections. 



The extreme length of conus is I mm. in the mid-ventral line 

 and 1.5 mm. in the mid-dorsal and lateral lines. The ventricle, 

 from apex to junction with conus, has a mean measurement of 

 5.5 mm. The proportion in mean length of conus to ventricle 

 is therefore I to 4. 



The conus contains two transverse tiers of valves, each tier 

 consisting of a right and left cusp placed symmetrically with re- 

 gard to the mid-sagittal plane. The general arrangement agrees 

 closely with that found in Tarpon, but the proximal cusps appear 

 to be proportionately more capacious. 



The conus in Megalops not only projects more freely from the 

 ventricle than in Tarpon, but is of greater proportionate length. 

 It would seem to resemble more closely the conus of Albula (as 

 described by Boas, 'So) except in the absence of the subsidiary 

 valve cusps of the latter. 



It should be noticed that the heart described is from a young 

 fish, also that the measurements are, at best, approximate ; there- 

 fore, comparisons with adults of other genera, if pushed too 

 closely, are apt to be misleading. 



The atrio-ventricular valve has three cusps. 



A specimen of CJianos cJianos (Forskal), for which I also have 

 to thank Professor Jordan, presents an easily recognizable ves- 

 tigial conus arteriosus, but only one tier of valves. 



ST. Louis, Mo., February I, 1907. 



