SHUMARD—BLASTOIDEA. 243 
their width is twice as great as at the base. p, angular 
mesial furrow extends the whole length of Pa fall? and on 
either side of this is a broad furrow, which coalesces with the 
sides before reaching the base. The fields consist of numer- 
ous pore and supplementary pore pieces, the former of which 
are transverse, gradually increase in width from below up- 
wards, and extend the while width of the field. They are 
somewhat wedge-shaped, their surface transversely excavated, 
and their inner extremities deeply and beautifully s 
~~ perpen ney pore pieces are very short, arched above, 
straight 
Pl sag interesting species occurs at the base of the —, 
——-. at Button-Mould Knob, seven miles south of 
Louisville, K. tucky. 
Rslsks ceihtitanconesspetl Summit of the Genus 
Pentremites—In 1850, the writer, in connection with Dr. D. 
D. Owen, announced in the Jour. of the Acad. of Nat. Sci., 
