PLATE 28. 



Fij. 1. 481. 1. Cyclonema cancell.4.ta. ( Png. 90.) 



1 a, b, e, d. Views of several specimens, showing an increasing size and slight variation in form. 

 1 e. View of the apcr(nre, the shell btinc slightly coniprcs.se<l in ;i vertical direction. 

 1 f, g. View of the front of the shell, and aperture of the .same. 



1 h. Portion of tlic surface enlarged, showing the character of tlio stria;. 



Fi?. 2. 482. 2. CvcLONEMA vf.ntricosa. ( Pag. 90.) 



2 a. Front view of the shell. 2 b. A'iew of the mouth. 



2 c. A portion of the surface enlarged, showing the character of the strite. 



Fig. 3 «, A. 483. 3. Cyclonema? obsoleta. ( Pag. 90.) 



Fig. 4. 4S.3. 1. Platyostoma. ( Pag. 91.) 



4 a. View looking upon the top of the spire. 



4 b. Profile view showing the slight elevation of the spire. 



4 c. Another specimen, view looking upon the spire. 



4 d. View of the aperture, which is angular at the outer margin, probably from pres.surc. 



Fig. 5. 484. 4. Cyclonema cancellata? ( Pag. 91.) 



.') a. Tlie east of the shell, which is smooth. 5 6. A portion of the shell from the base, enlarged. 



Fig. 7. 486. 16. Murchisonia subulata. ( Pag. 91.) 



7 a. A young specimen of this species. 7 6. An elder specimen of the same. 



I c, d. Two specimens of the largest size observed ; the last one wanting one or more of the upi)cr volutions. 



Fig. 8. 4?7. 8. Bucama stigmosa. ( Pag. 92.) 



8 a. Dorsal valve of an imperfect specimen. 



8 6. A portion of the same enlarged, showing the elevated decussating striic, and another portion where 



these are obliterated by abrasion or exfoliation. 

 8 c. Dorsal view of a cast of this species, with the apeiture and a part of the last volution broken olT". 

 8 d. Lateral view of the same specimen. 

 8 e. Transverse section of the last volution, where broken off. 



Fig. 9. 488. 9. BucANiA? bella-i-uncta. (Pag. 93.) 



Fig. 10. 396. 7. BncANiA TRiL0B.\TA. (Pag. 93.) 



10 a. A specimen, natural size. 



10 6. A large individual, much compressed in a longitudinal direction. 



Fig. 11. 4S9. 3. Oncoceras subrectum. (Pag- 94.) 



II n A lateral view of the fragment. 



11 b. A portion of the surfiice enlarged, showing a suture on one side. 



Fig 12. 494. 1. CoRNULiTEs flexuosus. ( Pag. 98.) 



12 a. A specimen, somewhat tortuous in form and partially compres.sed, covered with the external striated 



•shell. 

 12 c. A specimen, nearly entire, exhibiting the usual form and surface characters of this fossil. 

 12 d. A fr.agment of a si)eeimen more curved than usual. 



12 c. A longitudinal section of the last, showing the tube filled with (Vagmcnts of erinoid.s and shells. 



Fig. 13. 495. 1. DiscosoRUs conoidei-s. ( Pag. 99.) 



l.S a. One of these bodies of the natural size, preserving eight or nine rings from the apex to the base. 



13 6. The base of one of these discs from another individual. 



13 c. A. section of one of these discs exposed by fracture, showing the radiating and fibrous structure of the 

 body. 



