266 DAVEXrOET ACADEMY OF NATURAL SOIEXCES. 



Cyrtina appears in numbers, some no larger than a kernel of wheat. 

 There is no end to the young of Strophodonta demissa, Strophodonta per- 

 plana. Orthis vanitxemi, Spirifera suh-attenuata, etc. The most frail coral- 

 line forms generally preserved only on the surface of the hardened shale, 

 fronds of Fenestella, Ptylodiclya and Tentaculites here lie loose in the soft 

 matrix. These tender children of the Hamilton have been so cared for 

 and kindly protected through ages, that to-day in these reservoirs may be 

 obtained more numerous specimens of the young, and in a finer state of 

 preservation, than from the same area in any natural exposure of the rock 

 itself. It is a simple question : With no marked natural exposure of the 

 shale about us for miles, how and whence came this shale into its present 

 position y The nurse is here the rough old Helderberg^ holding the children 

 fondly and lovingly to her bosom ; but the mother herself is absent, and 

 has been for ages. 



It is mainly in their fossils that these beds present especial points of inte- 

 rest. I have had occasion already to speak of the Bens.seUceria as they form 

 continuous reefs of more than a foot in thickness, or as their broken 

 valves lay scattered on the surface of the upper layers, extending down- 

 wards to the depth of three or four feet. In addition to this abundant 

 fossil, and in the same beds, have been found the remains of Crinoidea 

 in great numbers. It is only within a short time that two have been 

 found in such state of perfection as to warrant a full description. These 

 forms are all limited to the uppermost beds so well defined on this side 

 of the river. Undei'neath these we find a rock corresponding to the dis- 

 puted beds between Moline and Rock Island, and common to all the 

 quarries we have examined. On lithological grounds alone the two 

 would be pronounced equivalents, while some of the same fossils are 

 found in both, serving still further to identify them. In this rock are 

 found Gypidula laeviuscida, Hall, Spirifera subundifera, Wortheu, Calceo- 

 criniis Barrisi, Worthen, and Phrugmoceras Walshii, Worthen. A Cono- 

 cardium has been found in marking and size so similar to Conocardium 

 trigonale, Hall, that there is scarce a doubt of its identity. Of unde- 

 scribed fossils, part of which are now in process of description, we have 

 three species of Crinoidea, the remains of Ganoidea, a large Trilohite, 

 one Rhynchonella, two Gyroceras, and one Avicida'. In addition are quite 

 a number of fossils in too poor condition to admit of description, mainly 

 casts. Among these are the genera Euomphalus, Bellerophon, Platyos- 

 toma, Orthoceras, Gompihoceras, and Platyceras. 



It is a remarkable fact that of the whole number of fossils thus far 

 enumerated, not one, in this locality, is found in either of the two divisions 

 Prof. Worthen describes as fairly representing the Hamilton C4roup. 

 Prof. Hall recognized the rock as containing '' few fossils," neither iden- 

 tifying old or describing new species. Prof. Worthen published that no 

 fossils were found in it differing from the Hamilton. This was a neces- 

 sary result at the close of the respective State Surveys, of which they were 

 the Geologists in charge. The quarries since opened have furnished 

 facts then unknown. The following list of fossils are found in the rocks 



