rllK.MiCAI. CO.Ml'OSl ri(>N OK IKIJNION I.IMKSTUNE 1 .' 



)/ 



lime (CiiO) (out of n possible 56 per cent), less than 0,5 per cent of inii<f- 

 nesia (^^L^0), less than 1 i)er cent of iron and alumina, and 1 to 2 per 

 cent of silica and other insoluble matter. The less pure limestones con- 

 tain larger amounts of silica and of iron and alumina, a part of the silica 

 being probably due to the presence of sand. 



In the transition to the overlying Hudson River series, beds of exceed- 

 ingly variable chemical composition may be found. The composition 

 of the calcareous shales, so widely used for the manufacture of Portland 

 cement, is approximatel}'' as follows : 



SiOj 10.2 to 20.5 per cent. 



^^^^^•' \ 5.4 to 7.9 i)er cent. 



CaO 39.7 to 44.8 per cent. 



MgO 0.4 to 1.4 per cent. 



Trenton Faunas in New Jersey 

 the faunal succession 



Several distinct faunal zones have been recognized in this formation. 

 Its outcrops, howQver, are so isolated and are usually so fully covered 

 with debris that fossils can be collected only from loose fragments of the 

 limestone on the surface. It is also rare to find more than a single 

 faunal zone in any one outcrop. Under these circumstances the deter- 

 mination of the exact succession of the faunal zones is a problem of 

 some difficulty. The investigation of the succession of these zones has 

 been only just begun, and further stud}^ will undoubtedly add much to 

 the results which can be announced at the present time. Enough has 

 been determined, however, to suggest a general correlation between the 

 Trenton formation as it occurs in New Jersey and New York. 



The lowest definite horizon in the Trenton at which fossils have been 

 found occurs at a locality a little over two miles southeast of Newton.* 

 The basal conglomerate is but slightly developed, or is wanting at this 

 locality, and in a bed lying but a few feet from the Kittatinny limestone, 

 the following fossils were collected : 



1. Streptelasma profunda (H..). 6. Bumastus trentonensis {'Emm.). 



2. Strophomena incurvata (Shep.). 7. Calymmene senaria Con. 



3. Ctenodonta nasuta (H.). 8. Arges? sp. undet. 



4. Hormoioma gracilis {H..). 9. Leperditiafabulites [Con.). 



5. Orthoceras sp. undet. 



*The exact locality is on the northwest slope of the 663-foot hill, about three-fourths of a mile 

 north of the southwestern end of Iliff' s pond. Sheet 1, New Jersey Topographical Atlas. 



