PLATE XX 



KETICULARIA BICOSTATA, vai:. FETILA Hall (Pagks 380-382) 



Fmi EKS 1, III. — The youngest example observed, and outline profile 

 of the same. 



FiGUKE 2. — Dorsal view of a largi' specimen. 



FiGUKi-; 3. — Cardinal view of the same. X 3. (11//; Rrpl. State GeoL 

 Iwl., pi. 27, figs, s, 9.) 



SrilUFKR CTKSPl S, VAK. SIMPLEX Hall (PA(ii:s 380-382) 



FiGURK 4. — Uorsal view of the youngest .growth-stage observed. 

 Within the single growth-lini', the smooth sub-circular initial shell is 

 visible, but outside this the shell has developed the median fold and the 

 surface fim)iri:r. 



Figure -la. — Outline profile of the same. 



FKii'RE 5. — Dorsal view of a mature individual. X 2. 



Figure ."j». — Profile of the same, {'l^lh Ann. Rf/it. M. Y. SliUc Mas. 

 Nat. Hi^t., pi. 2t, tigs. 1, 4.) 



SPIRIFEU ClllSPUS HisixGER (Pages 3f>0-3S2) 



Figure 6. — Dorsal view of a young form, in which the deltidial 

 plates are in an incipient condition. 



FiGUKE (Jii. — Outline profile of the same. 



Figure 7. — Dorsal view of a mature specimen. 



FiGiKK 7a. — Profile of the same. (28^/t Ann. Bept. N. Y. Slate Mus. 

 Nat. Hist., pi. 21, figs. 8, 12.) 



SPIRIFER NIAO.VRENSIS Conrai. (Page 385) 



Figure 8. — The cardinal area of a ventral valve, from Lockport, 

 New York. The deltidial plates are in the third stage of development; 

 the foramen not yet enclosi'd, but confluent with the hiatus below the 

 basal edges of the plates. Natural size. 



