LOWER CRETACEOUS FORMATIONS AND FAUNAS 597 
age collections, one is impressed with the excessive preponder- 
ance of the Aucelle, so far as number of individuals is 
concerned. In many places they are so abundant that they 
must have actually monopolized the sea bottom, crowding out 
everything else. 
‘Considering the fauna as an assemblage of species, the pro- 
portion of brachiopoda, though there are so few, is somewhat 
greater than in other American Cretaceous faunas. Among 
the mollusca the variety of forms of Turbinide is noteworthy. 
The proportion of ammonoids is also quite large, and there is 
an unusual development of the genus Hoplites.”’ 
The Aucellz.do not pass above the Knoxville, or to speak 
more accurately, the top of the Knoxville is drawn at the upper 
limit of the Aucella beds. Several other Knoxville species, how- 
ever, do pass up into the succeeding Horsetown fauna. This 
fauna has not yet been revised and a considerable number of 
undescribed species are known in recent collections, but the fol- 
lowing lists, though incomplete, will give a correct idea of its 
general character. In the lower part of the Horsetown ammon- 
ites are locally very abundant, the genera Lytoceras and Phyl- 
loceras being especially well represented in individuals. The 
following species occur in this portion of the series: 
Pentacrinus sp. Potamides diadema Gabb 
Rhynchonella sp. Helicaulax ? bicarinata Gabb 
Pecten operculiformis Gabb Actzon impressus Gabb 
Plicatula variata Gabb Lytoceras batesi (Trask) 
Avicula whiteavesi Stanton Phylloceras onoense Stanton 
Inoceramus sp. Hoplites remondi (Gabb) 
Nemodon vancouverensis (Meek) Olcostephanus traski (Gabb) 
Trigonia equicostata Gabb Desmoceras hoffmanni (Gabb) 
Trigonia leana Gabb ? Crioceras latus Gabb 
Opis sp. Crioceras percostatus Gabb 
Eriphyla sp. Ancyloceras remondi Gabb 
Protocardia sp. Helicancyclus zquicostatus Gabb 
Pleuromya papyracea Gabb Diptychoceras levis Gabb 
Lunatia avellana Gabb Belemnites impressus Gabb 
The few fossils that have been collected from the middle 
portion of the Horsetown do not show any decided change in 
