70 CARBONIFEROUS AMMONOIDS OF AMERICA. 



McCoy grouped all three under G. sphcericus, aud de Koninck united G. 

 crenistria with G. striatus. 



Occurrence. — Goniatites crenistria is common in the upper ^jart of the 

 Lower Carboniferous in Great Britain, Belgium, and Grermany. It has 

 been described under the name of Glyphioceras incismn Hyatt from the St. 

 Louis-Chester stage, of Texas (see PI. X, figs. 12-16) and Arkansas, 

 associated with Goniatites striatus {z=Glyphioceras cumminsi Hyatt (in the 

 Bend formation of Texas, and the Spring Creek limestone, so-called 

 Fayetteville shale, of Arkansas. 



The specimens figured on PI. XIV; PI. XV; PI. XVI, figs, la-j; and 

 PI. XXVI, figs. 1-3, came from Moorefield, Arkansas, from calcareous 

 nodules in shales. They were associated with an undoubted St. Louis 

 fauna. The specimen figured on PI. XXVI, fig. 5, came from the same 

 formation, near Boles, Ark. 



On account of the great interest and importance of this species, there 

 is given below the complete ontogeny of the American Goniatites crenistria 

 Phillips, var. incisa Hyatt, based on specimens from the St. Louis stage of 

 Moorefield, Ark., associated with, an undoubted St. Louis fauna. The 

 development of this species was first published b}' the writer in a paper in 

 the Proceedings of the California Academy of Sciences," from which 

 paper the following descilption with some modifications is taken: 



LARVAL STAGES. 



In order to obtain the larval .stages of Goniatites crenistria, a number of adults 

 were selected, so as to make sure of the identity, and the outer coils were broken off 

 until the desired size was obtained. This necessitated the destruction of several 

 specimens, but was M'ell worth while in view of reliability of the results. The 

 specimens were .studied in three different mountings, dry on cardboard, in a chop of 

 water on cardl)oard. and in water in a watch glass over a strong condensing lens. In 

 the hrst way the surface markings are seen best, in the second the sutures and form, 

 in the third the internal structure when the specimen is translucent. The nomencla- 

 ture used is that of Hyatt, published in Phylogeny of an Acquired Characteristic. 



PhyJeinhryonic. — The protoconch represents the first shell secreted by the shell 

 gland, and must have been formed while the animal was in the egg. It is quite 

 possible that some of the chambers were formed before the egg was hatched, but 

 this can not be determined on fossils. The protoconch is taken for convenience to 

 represent the phylembryonic stage of growth, the end of the embryonic, when the 

 class or phylum can be determined and the animal is already a cephalopod. In shape 



"Proc. Cal. Acad, .'^c-i., 3d series, (reolosjv, Vol. I, Xo. 3. 



