GEOLOGY OF OGDENSBURG 47 



In regard to their fossil contents also, the comparatively few 

 forms which are abundant seem to run through the whole section, 

 and fossil zones which are sufficiently restricted and sufficiently 

 individualized to serve as markers for a particular horizon in the 

 formation do not seem to be common. Ulrich went over the section 

 from Morristown to Ogdensburg with us, collected fossils from it 

 which he has compared with the material in his own large collections 

 from Missouri and elsewhere, and generously contributes the 

 following report upon them. 



Zone I (zone 4 of Ulrich's section, zones 1-3 being in the 

 Heuvelton beds below) of fossils from the quarry section of the 

 lower beds, given on page 40, and chiefly from the thin-bedded, 

 upper portion : 



L i n g u 1 a sp. undet. 



"Ophileta" grandis Ulrich. A widely distributed species 

 marking the Roubidoux (basal Canadian) formation in Mis- 

 souri. Shell larger, whorls expand more rapidly, and carina 

 more nearly peripheral in position than in O. compacta 

 Salter (=0. complanata Whitfield, not Vanuxem). 



Generically undetermined trilobite. (Collected by Chad wick, 

 only one specimen seen.) 



This is not the lowest fauna of the formation, since the heavy, 

 blue beds beneath contain a fairly abundant fauna, which is, how- 

 ever, difficult of collection and determination, since seen only on 

 glaciated surfaces. The species seem the same as those of zone 2. 

 My own collection shows that **Ophileta" compacta 

 Salter occurs in zone i, in addition to the forms listed. 

 "Ophileta" grandis Ulrich is the commonest fossil, 

 however. 



Zone 2 (zone 5 of Ulrich), the blue beds which follow above 

 the thin-bedded dolomites of the previous zone, and are crammed 

 with fossils, usually poorly preserved (plate 4). 



Tryblidium cf. ovatum Whitfield 



Maclurea (?) cf. transitionis Billings 



Maclurea (?) cf. oceana Billings 



Maclurea (?)cf. affinis BiUings 



Liospira (?Ophileta) aflf. hunterensis Cleland 



Liospira (?Ophileta) sp. cf. Raphistoma 

 praevium Whitfield 



Liospira sp. 3 (has more rapidly expanding whorls and 

 smaller umbilicus than two preceding species) 



"Ophileta" compacta Salter 



