S5Q Keport of the State Geologist. 



Spirifer mucronatus, Conrad, var. posterus, 



Plate 7, figs. 20-24. 



Spirifer mucronatus, Conrad, var. posterus, Hall. Palaeontology of N. Y., 

 . vol. VIII, pt. 2, p. 361, pi. xxxiv, figs. 27-31. 1894. 



A late variety of the typical Hamilton form, characterized by 

 its small size, usually narrow bodies and acuminate cardinal 

 extremities. 



Chemung group. Tompkins county, If. Y. 



Spirifer disjunctus, Soweeby, var. sulcifer. 



Plate 7, fig. 27. 



Spirifer disjunctus, Sowerby, var, sulcifer, Hall. Palaeontology of N. Y., 

 vol. VIH, pt. 2, p. 361, pi. XXX, fig. 16. 1894. 



This variety is distinguished by the sharply defined median 

 sulcus on the folds of the brachial valve. It has heretofore been 

 embraced within the limits of S. disjunctus, but the character 

 referred to appears to be persistent. 



Chemung group. JVear Olean, JV. Y. 



Spirifer Williamsi. 



. Plate 7, figs. 17-19. 



Spirifer Williamsi, Hall. Palaeontology of N, Y., vol. VIII, pt. 2, p. 361, pi. 

 xxxvii, figs. 20-22. 1894. 



Shells of the form of Spirifer increhescens, Hall, and varying 

 but little in size. Median fold and sinus well developed. The 

 latter bearing usually three, sometimes four plications, finer than 

 those on the lateral slopes. Of these the median plication is 

 generally the strongest. This, however, is not always the case, 

 the arrangement of these plications being frequently quite irregu- 

 lar. The median fold generally bears a median groove and one 

 lateral plication on each side. On each lateral slope of the shell 

 are seven or eight plications. 



A normal example measures : Length, 15 mm. ; width on hinge, 

 2i mm. 



Chemung group. Allegany county, If. Y. 



