150 Annals of the Carnegie Museum. 



at the top and bottom, and such layers recjuire constant scrubbing and 

 breaking to allow the acid to act. The fossils seem equally well silic- 

 ified in both, but are not obtained in perfect condition from the latter 

 owing to the mechanical difficulties. The lithologic character of 

 the rock indicates rather shallow water and a sufficient distance 

 from the shore line to prevent a mixture of sand or gravel. The 

 fossils themselves show that their habitat was free from any violent 

 wave action or strong currents. This is indicated both by the state 

 of preservation, which is remarkably fine, and the presence of large 

 numbers of species and individuals of Bryozoa. Large fronds of 

 the delicate species like those of the Fenestellidae are often found and 

 such delicate spines as those of Chonetes and Strophalosia are beauti- 

 fully preserved. 



With the exception of the phosphatic linguloid shells and a few of 

 the pelecypods, all kinds of shells are well silicified and by this method 

 of collecting practically everything in the rock is preserved. This 

 accounts for the large number of species found, and for the great 

 number of individuals of species usually called rare. Fholidops Jiam- 

 iltonensis, usually not considered abundant, is represented by over 

 1,500 specimens in the present collection, being second on the list 

 of most common species. By far the most common one is Chonetes 

 sciiiihis, of which about 3,500 specimens have been picked out. 

 Another feature is the abundance of ostracods, of which there are 

 above 15 species, 11 of which have been identified so far. 



New species, with the exception of a new Chone/es, are confined to 

 rare genera, and will not be described at present. 



List of Species. 

 Anthozoa-Actinozoa : 



Heliophyllum ha Hi, R.' Ceratopora dichotoma, c. 



Michelinia stylopora, r. Cerafopora Jackson/, c. 



Aiilopora serpens, c. 

 Vermes : 



Spirorl>is anj^uPafns, R. CornuUtes w. s., r. 



vS". spinulifera, a. Autodetus lindstrxnii, c. 



CornuUtes liamiltonicE, c. Autodetus n. s., R. 



' According to the usual custom the ablireviations R, r, c, and a, are used here. 

 A' signifies that the species is very rare ; ;', rare ; c, common ; a, abundant. 



