PLATE XLVII. 



Ctbtooeras (Gohphoceras) mexula. 



. PageSeo. 

 See Plate 111, 

 Fig. 1. Ventral view of a chambered fi-ag-ment, showing the enlargement of the tube and the depth of the 



air-chambers. 

 Fig. 2. Lateral view of the preceding, showing the amount of the curvature of the tube. Upper Helderberg 

 limestone. Clareiice Hollow, N. Y. 



OtETOCERAS M0R8UM, 



Page 3ii7. 



Fig. 3. Ventral view of a fragment which is imperfect at the apex, showing traces of the transverse costa 



of the test and the slight sinus along the ventrum. 

 Fig. 4. Lateral view of the preceding, showing the curvature of the tube. This specimen is the type of the 

 species, and is fi-ora the Upper Helderbei'g limestone. Clarence Hollow, N. Y. 



CtRTOCERAS EOQENIUM. 

 Page 369. 

 See Plates 36, 96, 97. 

 Fig. 5. Lateral view of an individual nearly entire, showing the straight outer portion and curved apex. 

 Several fragments of the test, preserving the surface-markings and ornaments, are adhering to 

 parts of the tube. The internal mould preserves the furrows of the crenulations and the annu- 

 lations marking the exterior ridges of the test. 

 Fig. 6. Ventral view showing the sinus of the ornaments and apei'ture, with the variation in the prominence 

 and frequency of the annulations and transverse ridges toward the apex and near the aperture. 

 Fig.V. Dorsal view of the sti-aight portion of a large individual showing a slight gibbosity, due to the 

 gradual contraction of the tube toward the aperture. The dorsal margin of the aperture is 

 shown to be continuous and entire. In this example the prominent expansions of the test 

 become obsolescent toward the aperture, where the shell is marked by lamellose lines of growth. 

 These specimens are from the Upper Helderberg limestone, at Schoharie, N. Y. 



GtROCERAS 8P1NOS0M. 



Page 382. 



See Plates 48, 49, 98, 99. 



Fig. 8. Ventral view of a compressed specimen, showing the nummuloid elements of the siphuncle, as exposed 



in the process of weathering. Schoharie grit. Scholiarie, N. Y. 



