PLATE LXXXIL 



Orthoceras pacator. 



Page 307. 



Fig. 1. A fmpnent of a, lurpe individual embracing' a portion of the tube near the chamber of habitation, 

 ajid showinff considerable irregularity and variation in the depth of the air-chambers. The 

 8i>ecinien is much flattened fi-om compression in the soft shales, and many of its features 

 obscured. Portage group. Mt. Morris, Livingston county, N. Y. 



Pig. 2. A fi-agmeut of a small, compressed individual, showing the constriction of the tube near the aper- 

 ture, and a curvature ami obliquity of the sutures, due to compression. 



Fig. 3. An incomplete individual retaining its normal proportions, and showing the chamber of habitation 

 nearly entire. The last two air-chambei-s are not shown in the tigui-e, making the chamber of 

 habitation appear longer than its true proportions. 



Fig. 4. A septum of a larger individual, refen-ed to this species with doubt. The tube is somewhat com- 

 pressed on one side, and the true position of the siphuncle is not shown. From a septum of 

 specimen figure 3, it is seen that the siphuncle is more excentric than is here repi-esented. 



Fig. 5. A septate portion, showing the regular increase in the depth of the air-chambers from the apex, and 

 their irregularity near the <mter chamber. Portage group. Ithaca, N. T. 



Fig. 6. A fi-agment of the chamber of habitation, with several attached air-chambers, showing the inequality 

 of the last air-chamber. Portage group. Ithaca, N. T. 



Orthoceras, sp. indet. 



Fig. 7. A fragment of undetermined, specific relations, whic'i has been incrusted with a Bi-yozoan of peculiar 



character. 

 Fig. 8. A portion of the surface enlarged, Bhowing the epitheca and bases of the cell-pores, as exposed upon 



a weathered surface. 



Ortooceras ANGUIS. 



Page 312. 

 Fig. 9. A compressed fi-agment, showing the gradually enlarging tube, and the regular, traiisverse, 

 lamellose striie of the sui-face. Lower part of the Chemung group. CascadilUi Greek, Upper 

 Fidl, Ithaca, N. T. 



Orthoceras Atreus. 



Page 305. 

 See Plate 88. 

 Fig. 10. A chambered fragment, preserving its natural cylindiical form, and showing the depth of the air- 

 chambers. Calcareous beds of the Portage group at Penn Yan, Yates county, N: Y. 

 Fig. U. A septum of a small fragment, preserving several chambei-s, and showing the size and excentric 

 position of the siphuncle. The specimen is refen-ed to this species with some doubt. 



