NOTES ON THE EARLY STAGES OF CERTAIN GONIATITES. 



By John ML Clarke. 



Some Points in the Development of Anarcestes plebeiformis, Hall (sp.). 



Goniatites plebeiformis was described by Professor James Hall, in Palae- 

 ontology of New York, vol. v, part 2, page 448, 1879, and illustrated on plate 

 cx, figs. 3—9 of that work. It had been previously figured under the name of 

 Porcellia? rotatoria, Hall; in the "Illustrations of Devonian Fossils," pi. xvi, 

 figs. 25, 26, 1876, and these figures are also reproduced on plate xvi of the 

 former work. It is a rare and heretofore imperfectly known sjiecies, all the 

 specimens having been obtained at a single locality, Cox's Falls, near Cherry 

 Valley, N. Y., in a thin layer of impure limestone belonging to the epoch of 

 the Marcellus shales (lowest middle Devonian). The species is especially 

 interesting because of its primitive characters. It is in all respects a typical 

 Anarcestes, as will be seen upon consulting the figures of whorls and septa 

 as cited. 



In its usual mode of retention only the outer whorls of the shells are 

 preserved ; hence no illustration has been given of the character of the inner 



Figures 1, 2. Anarcaite* flibeiformis. Fig. 1. The distal end of the proteconch, showing its striated sur- 

 face, i 25. Fig. 2. Frent view of the nepionic shell, showing the projecting ends of the protoconcb. x 25. 



whorls except in a single instance based on an external mould. The impure 

 limestone is nodular and the outer parts of the shell may be filled with the 



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