295] B. Wade 97 



and a Cyprimeria is 4^/ 2 inches. Exogyra costata and Gry- 



phaea vesicularis occur in their typical massiveness. The 



shells of Cucullaea, Crassatellites and Veniella are very 



abundant and evidently belonged to three very thrifty groups 



of Mollusca which lived under conditions especially suited to 



the secreting of calcium carbonate. The afflorescence of the 



Volutidae in the Upper Cretaceous has already been empha- 



sized. All the species of this family are above medium size 



and many of them are very large. Perfect specimens of 



Volutoderma in the collection attain an altitude of half a 



foot. There are broken specimens which when perfect must 



have been almost a foot long. Volutomorpha is probably the 



giant of the Cretaceous gastropods. There is a fragmenl 



of several whorls of the spire of one species of Volutomorpha 



in the collection which would probably be 18 inches in length 



were the specimen complete. The genus Ptychosyca is large 



and inornate while the genus Drilluta is elongate and elabo- 



rately sculptored. The shells of Pugnellus and Gyrodes seem 



to be relics of once prosperous organisms which saw no 



hardships in life. Lwpeplum, Lunatia, Xancus, Hydrotri- 



~bulus, Ornopsis, etc., though less in dimensions than some of 



the above forms, evidently grew in very favorable environ- 



ments. Species of such genera as Columbellina, Solariella, 



Act eon, Cerithium, etc., are much smaller in size, yet their 



shells are thick and stout, and no doubt grew where condi- 



tions were favorable for secreting calcium carbonate. The 



bivalves also show various ranges in size of thick, stout shells. 



The Cephalopoda were the largest of the Coon Creek Mol- 



lusca. The genus Eutrephoceras is abundantly represented 



by large thick-shelled cavernous individuals more than six 



inches in diameter. One species of Baculites is very abundant 



and large. Although no complete, large individuals have been 



recovered from the matrix, there are several large pieces of 



shells and body chambers in the collection from 6 to 18 



inches long and restorations of these show that some indi- 



viduals were five feet in length. It should be noted here that 



while most of the Upper Cretaceous molluscs had thick stout 



7 



