MUSEUM OF COMPARATIVE ZOOLOGY. 



Ill 



EXPLANATION OF SIGNS USED IN THE PLATES. 



A. Ovisac. 



B. Ovishell. 

 C Whorls. 



lc. First whorl. 

 2c. Second whorl. 



D. Shell. 



d\ Lining layer. 



d". Median layer. 



d'". External layer. 



d + . Black deposit or layer of the hood. 



E. Septum. 



le. First septum. 

 2e. Second septum. 



F. Abdominal lobe. 



G. Lateral lobes. 



g. Superior lateral lobes, 

 g". Inferior lateral lobes, 

 g'". Auxiliary lateral lobes. 

 H. Dorsal lobe, 

 h'. Superior dorsal lobe, 

 h". Inferior dorsal lobe, 

 h''. Auxiliary dorsal lobes, 

 h. Minor lobes. 



J. Abdominal cell. 



K. Lateral cells. 



k'. Superior lateral cells. 



k'\ Inferior lateral cells. 



k'". Auxiliary lateral cells. 



L. Dorsal cell. 



1'. Superior dorsal cells. 



1". Inferior dorsal cells. 



I'". Auxiliary dorsal cells. 



M. Marginal lobes. 



N. Marginal cells. 



O. Siphonal fissure. 



P. Siphonal collar. 



P. Siphonal funnel. 



Pi. Siphonal coecum. 



S. Siphon. 



s'. Horny layer of siphon. 



s". Accessary layers of siphon. 



s'". Sheath. 



U. Embryonal umbilicus. 



y. Cone of the siphonal coecum. 



X. General mark. 



