622 The American Naturalist. [July. 
closely allied nevv species from the blue shales below the Devonian 
limestone at Independence, Iowa. A critical study of all these forms 
showed them to be generically distinct from Pachyphyllum, and to 
constitute a new and well-marked genus. We have also personally 
collected from these shales three new specimens of Pachyphyllum, all 
of which are described in this paper, thus making "four species of this 
genus known to occur in American strata. 
The occurrence of the American representative of this genus only 
in the Rockford shales of lowa^ (so far as known) is a fact worthy of . 
note. This fact, together with many others now in our possession, 
tends to widen the breach between its supposed equivalents, the Che- 
mung group of Hall and Whitfield,* and the Hamilton group of Dr. 
White.5 
Pachyphyllum ivoodmani White,— Compare with description of Hall 
and Whitfield; (23 Ann. Rep. New York State Cabinet, p. 231.) 
Coral variable ; growing in irregular, flat, convex, hemispheric, oblong 
or semi-circular masses, from single beds three to four mm. in height 
to corallums twenty-five and one-half centimetres in diameter. Cell 
walls, more or less strongly exsert, projecting from less than one mm. 
to more than eleven mm. above the intervening spaces ; from three 
very unusual). Very often situated at one extremity of the area, and 
rising perpendicular or obliquely to, or even lying flat upon, the sur- 
face of the inner cellular space ; wall thin or of moderate strength ; 
central depressions very irregular, circular, oblong or ovate in outline, 
from one and one-half to five mm. in depth. Rays numbering from 
twenty-five to forty-one, about half of which extend to the elevation 
or columella in the centre, while the remainder terminate just within 
the inner wall. Entire cell from three mm. to about two centimetres 
in diameter, partially limited by a wall formed by the coalescing of 
the costae from the adjoining cells. Intercostal and interseptal spaces 
divided by numerous thin partitions. Usually the great size to which 
the exsert iX)rtion of the cells sometimes attains is at the expense of 
vertical height; and likewise when a great hti-ht is attained, it is at 
heavy cost to diametrical proportions, in isolated cases the under 
surface and margin of the corallum exhibit small i)atches of epithecal 
crust ; and in still more isolated examples, where the exsert portion of 
1 the Devonian limes 
