CiLVPlIIUCERAS. 63 



reaching' a greater diameter thnii (i nun.; it is ovolntc, lias wide Ojjeii 

 umbilicus, low tlattened w-liorls with ti-;i])cz(ii(hd cross section, taint umhili- 

 cal rihs which reach almost to the abdomen. There are about three rather 

 faint constrictions to a revohition. 'I'lie surface is ornamented only with 

 fine smooth cross stria;. The sejjta are Hke those tig-ured by de Koninck; 

 the differentiation into two external lobes has not taken place, as in the rest 

 of the section Glijphioceras, but it is indicated liy the incipient ventral 

 saddle. These are certainly persistent larval characters, and the so-called 

 species maybe merely a case of arrested development such as is seen in the 

 3'oung- of (Tlypliwceras diadema, but whether it is really the young of some 

 other species, or whether it is a separate form, can hardly l)e determined as 

 yet. At any rate the adult of Glyphioceras nmtabile has not been found in 

 America, and the American form can hardly be the young of that species. 

 Nor in the beds where it occurred have any other species with similar 3^oung 

 been found; in fact no other species oi Gbjph.ioceras has been found there at 

 all. To the writer it seems quite possible that G. calyx is onlv the male of 

 some species of the group of Goniatites striatus, since in England, Belgium, 

 and America it is associated with this group, and more esjieciallv because 

 the young stages are exactly alike in these. A demonstration of this is at 

 present impossible, for we know nothing of sexual variations in the 

 ammonoids. 



Occurrence. — The specimens figured here are deposited in the geologic 

 collection of Leland Stanford Junior University, California, and were found 

 in the Lower Carboniferous, St. Louis-Chester stage, Fayetteville shale, 

 at Moorefield, Ark., associated with Goniatites crenistria Phillips, and many 

 other species of invertebrates characteristic of this horizon. In Europe the 

 species is found in the Vise horizon, in England, Belgium, and (lermany. 



? GrLYPHlOCERAS DIADEMA Goldfuss. 

 PL XII, %. 10. 



1837. AiJiiininltex diaderiiii ((Toldfuss). H. K. Beyrich. De (roiiiatitis. |). 1."). PI. II, 



figs. S-IO. 

 1837. Aiiiiiioii'itcx lister!, H. E. Beyrich, Beitr. •/,. Keniit. Khciii. Uel)ergaiigsgel). , 



p. 14, I'l. II, figs. 6a-b, and 11. 

 IS-tii— 14. ^linmon.iten dkulema, L. G. de Koninck, Descr. aniin. foss., ]>. 574. PI. L, 



figs, la-f, 2a-b. 

 1845. Goniatiti'x dladema, Murchison, Verneuil ;uid Kevsciliiiy. (ri'ol. Itussie 



d'Europe. etc., Vol. II, p. 3(;7, PI. XXVII, figs. la-d. 



