GONlOl.Or.OCKRAvS. 125 



GONIOLOBOCERAS WELLEKI Slllitll, sp. UOV. 



PI. XX, fi-s. 9-11: I'l. XXI, ri.-s. 1-6. 



This species was at iirst, thouo-lit Ijy the writer to be identical with 

 G. goniolobiim Meek, but it has the sides somewhat more flattened, is more 

 com[)ressed laterally, and at maturity has the ventei- narrow, angular, and 

 .slightly furrowed; also the ventral saddle is not notched, but has a tongue- 

 shaped forward extension. In G. goniolohum the siphonal saddle is narrow, 

 in (t. ivcllrri it is broad and rounded. These differences may be due to 

 individual variation or to incorrect drawing of Meek's type; but none of 

 the specimens before the writer varied in these respects. 



The adolescent stage (figured on PI. XX, figs. 9-11) of a young shell, 

 broken out of a mature si)ecimen from (Iraliam, Tex., shows the characters 

 of Muensteroceras, and proves that the genus is derived from a typical 

 member of the Giyjihioceratidae, for the shape of the shell, the wide 

 umbilicus, flattened sides, broadly rounded abdomen, constrictions, and 

 the septa all agree with that genus. 



The shell is smooth, compressed, with flattened sides and narrow 

 rounded venter at early maturity; aiigular and slightly furrowed at a later 

 stage. The umbilicus is very narrow, showing none of the inner whorls ; the 

 whoi'l is involute, deeply embracing, indented to more than one-third of its 

 height by the preceding whorl. Surface smooth, devoid of constrictions, 

 ribs, or other ornaments. The septa are angular and sinuous, slu)wing the 

 general character of the Glyphioceratidfe. Internal septa show the charac- 

 teristic sharp antisiphonal lobe and the tongue-shaped internal lateral on 

 each side, as do all tyi)ical members of the Glyphioceratidse. 



Occurrence. — The first specimen of this species was seen by the writer 

 in the paleontologic collection of the ^Yalker jMuseum, University of 

 Chicago, from the Upper Coal Measures of Montgomery County, 111. The 

 only other sj)ecimens known are from the Ujjper Coal Measures, Cisco 

 formation, of Graham, Young Countv, Tex., where they were collected h\ 

 A. B. Gant. Other specimens are in tlie private collection of the late 

 Prof. Alpheus H3-att, in the U. S. National Museum, and in the private 

 collection of the writei-, obtained on a recent visit to Graham. The genus 

 MUlcroceras of Hyatt is probably only the young of Gonioloboceras, but 

 not enough specimens are known at present to determine this. 



