160 Twenhofel and Dunbar — Nodules with Fishes. 



Fossil Content of the Nodules and Inclosing Shales. — The 

 fossils of the nodules are chiefly vertebrates. Those collected 

 consist of skulls, bones, and spines of fishes, a crustacean 

 (Palceoca?*is, probably new), one specimen of Nautilus cf. 

 j)lanovolvis, and eight pieces of wood, one of which shows 

 a great development of the medullary rays and another the 

 vascular bundles. There are no leaves, such as occur so abun- 

 dantly at the Mazon Creek locality, while invertebrates are 

 rare in the nodules, although quite common in the inclosing 

 shales. It was at first thought that some of the remains were 

 amphibian, but this view appears to be erroneous. About 

 eight hundred nodules have been broken open, and from these 

 more than one hundred and fifty vertebrate fossils of value 

 have been obtained. Many of the nodules carry what are 

 thought to be coprolites, some of them contain unidentifiable 

 fragments of bone, and a still greater number are apparently 

 barren. These figures' show that the locality is far more fos- 

 siliferous than that of Mazon Creek, where Doctor Moodie 

 estimates that there is one vertebrate fossil to every thousand 

 nodules.*" 



The vertebrates were submitted to Doctor Moodie, and 

 his identifications are as follows : — tooth of Cladodus, 

 teeth of Cochliodonts, two teeth of Diplodus, spine of 

 Ctenacanthus, dermal tubercles of fishes, fish coprolites, and 

 eighteen skulls of small fishes, whose systematic position has 

 not been determined. Three of the skulls contain remarkably 

 well-preserved casts of the brain — a feature of preservation 

 which Doctor Moodie states, " is unique in the history of ver- 

 tebrate paleontology." f 



The fossils of the inclosing shales are of a totally different 

 character. There are no vertebrates, nor any wood. The 

 invertebrates are not uniformly distributed, but are in patches. 

 They consist of small forms, forms with a more or less spheri- 

 cal shape, or forms with air chambers. All are of marine 

 origin. Those which have been identified are AxophyUum 

 rudei^) (rare), Meekella striatocostataiy), Orbiculoidea nitida 

 (r), Product us nebr ashen sis (r), Pugnax ?i^A (common), Belle- 

 rophon stevensanus (r), Trepospira sphwrulata (r), Edmondia 

 like nebraskensis (but with finer concentric striae) (r), Nautilus 

 planovolvls (r), Orthoceras sp., crinoid stems, and several 

 additional species of unidentifiable gastropods and pelecypods. 



In the brown shale above the nodule bed, there are also fos- 

 sils and nodules, the latter of lenticular shape, brown in color, 

 generally hollow, and altogether without fossils. The biologic 

 facies must have been quite different, since the fauna is mollns- 



* Moodie, this Journal, vol. xxxiv, p. 279, 1912. 

 f Moodie, personal communication. 



