PLATE LXXVIII B. 



OrTHOCBRAS MASCnLUM. 



Fig. 1. A fi-agiuent showing tho great depth of the chambers, and gradual enlargement of the tube. The 

 crenulations of the upper margin of the chambei- walls, impressed upon the interior cast, are 

 ebowa along the septal line of several of the chambei-s. Clarksville, N. Y. ' 



Orthoceras Pelops. 



Page 233. 



^ See Plates 35, 85 A, 37. 



Rg. 2. An individual of this species retaining a large portion of the chamber of habitation, and eleven other 



chambere. The sinuate direction of the strife iipon the chamber of habitation is not due to a 



proper sinus of the ornamentation, but to the repairing of a fracture in the shell, which had 



thus become thickened and is presei-ved, while the other portions are dissolved. Knox, N. Y. 



Orthoceras luxum. 



Page 2<4. 

 See Plates 35, 76, 77. 78, 81, 112. 

 Fig. 3. Longitudinal section showing the elements of the siphuncle, and amount of organic deposit. The 

 specimen is the same as the one figured on plate 77, figui-e 8, where the details are not suffi- 

 ciently or accurately represented. 



Orthoceras tetriccm. 



Page 261. 

 See Plate 80. 

 Fig. 4. A septate fragment pi-eserving the test as i-eplaced by the material of the rock. Several individuals 

 of a species of Spirorbis are attached to the upper portion. Clarksville, N. Y. 



Orthoceras Thoas. 



I'age 261. 

 See Plates 41, 79, 80, 112. 

 Fig. 5. A fragment retaining a large portion of the chamber of habitation and four other chambers 

 Remains of the sui-face-mai-kings are preserved on a portion of the tube. This specimen 

 illustrates the extreme variation in the pi-ominence and distance of the annulations. Clarks- 

 ville, N. Y. 



