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H. W. NORMS AND SALLY P. HUGHES 



secondary folds and related to the secondary nerve. Sund sug- 

 gests that the anterior secondary chamber corresponds to Jacob- 

 son's organ. Asai ('13) shows in models of the olfactory organ 

 of Mustelus laevis that the olfactory cup is divided by the mem- 

 branous fold into a posteroventral and an anterodorsal chamber, 



Fig. 4 A cross-section through the right olfactory cup, cutting through the 

 nasal opening and the extreme anterior edge of the lamellae of the posteroventral 

 part of the olfactory chamber. Section 346. X15. 



but that the two series of Schneiderian folds are continuous with 

 each other around the ends of the septum. 



In Squalus acanthias in the 150-mm. stage these two parts of 

 the olfactory cup are posteroventral and anterodorsal in position. 

 The olfactory fila entering the mesial (dorsal, mesial, ventral) 

 group of glomeruli in the olfactory bulb are related to the larger 



