PLATES AND EXPLANATIONS 



CEPHALOPODA. 



PLATE XXXV. 



Ortuoceras Pklops. 



Pago -233. 

 See Plates 35 A, 37, 78 B. 

 Fig. 1. A fragment, preserving a considerable portion of the chamber of habitation, showing a gentle con- 

 striction below the apertuie. The great convexity of the septum at the lower extremity of the 

 tigui-e is due to the flattening of the si>ecimen. Schoharie, N. Y. 

 Figs. 2, 2 a. A septate fragment, retaining its form and septa, without compression j 2, a section showing 



size and position of siphuncle. Helderherg tnountains. 

 Fig. 3. EiJargement of a portion of the test from specimen tig. 2. 



Orthoceras luxum. 



Pago m. 

 See Plates 76, 77, 78, 78 B, 81, 112. ( 

 Fig. 4. A cru.shed fragment, showing a usual ex.solute condition of the air-chambers. Schoharie, N. Y. 

 Fig. 6. A fragment of the septate portion of an individual, pi-esenting the characters of the organic deposit 



on each side of the carina, and on the ventral walls of the chambei-s. 

 Fig. 6. Same as the preceding, showing this feature in a less marked degree. 

 Fig. 7. A small fragment, retaining, in the cast, evidences of the lamellose-striate surface of the test. 



Orthoceras Tantalus. 



Page 241. 



See Plate S5 A. 



Fig. 8. A specimen retMning a portion of the chamber of habitation and fifteen air-chambers. The banded 



or zoned appearance, so prominent in 0. cbigvlv/m, is here m.uch leas marked. 

 Fig. 9. A septum of the jjreceding specimen, showing the size and position of the siphuncle, and the organic 



deix)sit on the septum around the si])huncle. 

 Fig. 10. Portion of a large individual, presenting the same features as specimen figs. 8, 9. 



Orthoceras carnosum. 



Pago 258. 



Fig. 11. Ventral view of a specimen retaining the grand chamber and ten of the air-chambers, showing the 

 surface characters and the sinus of the ornaments, ScMiarie, N. Y. 



