PLATE CVI. 



Nautilus cavus. 



Page 418. 

 Fig. 1. The concave doreal siile of a part of the outer chambered volution, showinjf the impression anil the 



sinuosities in the septa, caused by the i-e-entrant volution. 

 Fi(f. 2. The ventral side of the specimen, showing' the gi-eat depth of the air-chambers. 

 Fig. 3. Lateral view of the same, the open umbilicus and the curvature of the volution. ,From the shales 



of the Hamilton group. Near Cumberland, Md. 



Nautilus bucinum. 



Pago 412. 

 See Plates GO, 107, 109. 



Fig. 4. A lateral view of an imperfect sjiecimen which has been partially crashed somewhat obliquely in a 

 dorso- ventral direction. 



Fig. 6. The ventral side of the preceding specimen, showing the lateral expansion of the chamber of habita- 

 tion and ailjacent air-chambers. The surface is partially covered by a tubular parasite. 

 Casenovia, N. Y, 



Fig. 6. The ventral side of a specimen which preserves nearly its natural proportion, showing the deep and 

 gradually expanding chamber of habitation. The shell is partially preserved in a macerated 

 condition, and is marked by the impressions of branching tubular Bryozoans. The opposite 

 ride of the same specimen is shown on plate 58, figure 4. Sol^ville, Madison county, N'. Y. 



V\g. 7. A longitudinal section of a small specimen, which shows the depth of the outer chamber, with the 

 character and concavity of the attached air-chambers. Quarries north of Slierbume, Clunango 

 county, N. Y. 



Nautilus oribns. 



Page 420. 

 See Plates 61, 105. 

 Fig 8. A lateral view of a young or medium-sized specimen, showing the principal part of the chamber of 

 habitation, the depth of the air-chambers and the deep umbilicus. From the Marcellus shales. 

 Near RichmondviUe, Schoharie county, N. Y. 



