52 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



EXPLANATION OF PLATES. 



All the figures are camera drawings of specimens preserved and dehydrated in 

 alcohol and cleared in clove oil. 



PLATE 1. 



Fig. 1. Right side of the anterior end of Branchiostoma pelagicum Giinther. 



X 30. 

 Fig. 2. llight side of the posterior end of Branchiostoma pelagicum Giinther. X 30. 

 Fig. 3. Left side of the posterior end of Asyrametron lucayanum Andrews, from 



the West Indies. X 40. 

 Fig. 4. Left side of the posterior end of Asymmetron orientale, sp. nov. X 25. 



PLATE 2. 



Fig. 5. Heteropleuron agassizii, sp. nov. ; right side. X 5. 



Fig. 6. Heteropleuron parvum, sp. nov. ; right side. X 12. 



Fig. 7. Asymmetron macricaudatum, sp. nov. ; right side. X 10. 



