Contributions to Palaeontology. 37 



It is more strongly tubereulated tliJin E. coilatus, from which it is dis- 

 tinguished by its general form, as well as b}" the form and arrange- 

 ment of the plates. Plate II., fig. 9a, represents the form and strongly 

 tubereulated appearance of the species. Fig. 9 shows the plates of a 

 slightly compressed specimen, from which most of the tubercles have 

 been removed. 



The specimens illustrated were collected by C. B. Dyer, in the upper 

 part of the Niagara Group, at Waldron, Ind., and are now in his col- 

 lection. 



MiCRospoxGiA, n. gen. 



[Ety.— JZ/A-ros, small; spongia, sponge.] 



A free calcareous sponge, destitute of an epitheca. The texture is 

 finely porous, without large canals or openings on the surface. Spi- 

 cules (?) verv minute aud needle-shaped. 



MiCROSPONGIA GREGARIA, U. sp. (Plate II., fig. 2.) 

 l^iy .—Gregarucs, belonging to a flock ] 



This is a small gregarious, globular, calcareous sponge, free and hav- 

 ing no epitheca. Its structure is fibrous or minutely porous, and very 

 compact. Weather-worn specimens show the fibrous structure, which 

 is well illustrated in the figure. Microscopic sections, prepared b}^ Dr. 

 J. H. Hunt, reveal what we suppose to be spicules. They are minute 

 needle-shaped bodies. This species is sometimes found in clusters, 

 though it is by no means a common fossil. Specimens collected, vary 

 in diameter, from less than one eight to more than one half an inch, 

 and have been found at Cincinnati, and in the upper part of the Group. 

 The specimen illustrated is from the collection of C. B. Dj'er. 



Spirifera (?) AVALDRONENSis, u. sp. (Plate II., fig. 36, dorsal; fig. 3c, 

 ventral; fig. 3a, basal; and fig. 3, cardinal view.) 



Shell subquadrate and moderately ventricose; hinge line rather long- 

 er than the width of the shell; surface smooth or showing only concen- 

 tric lines of growth. 



Ventral valve somewhat p3'ramidal, with the apex, extending beyond 

 the hinge area and truncated b}- a circular foramen; arcuate below the 

 umbo, and curving rapidly to the base; area curving to the dorsal 

 valve, and becoming linear in the extension of the hinge line. 



Dorsal valve highh' elevated in the middle, and rapidly descending to 

 the margins, except at the cardinal angles, where it is flattened to pro- 

 duce the extension of the hinge line; apex incurved. 



The interior is unknown, and the triangular fissure, which should 

 mark the ventral valve, if the species is a true Spirifera, has not been 

 observed. 



