AGONIATITES, NOAI1SMOCEUA8. 33 



the sutures formiiiti' u low saddle upon the unihiliciil anylp. then gent!)' curving 

 V)ackward and forming on each lateral face a single broad lobe which occupies the 

 entire width of the volution; the direction of the suture upon the periphery can not 

 be certaiidy determined, hut there seems to be a low saddle on either side, with a 

 shallow ventral lobe Ijetween. Position of the siphunclc unknown. Surface marked 

 by faint lines of growth which are sinuate on the periphery of the shell. 



BeiiKirl's. — In the original description of Goniatites opiiiiKs. specimens of two 

 entirely' ditiereut species were apparently used, the general form of the shell being 

 described from one specimen and the sutiare from another. The specimen here 

 illustrated on PI. VII. fig. 8 [in Weller's Kinderhook Faunal Studies, II, The 

 Fauna of the Chonopeetiis Sandstone at Burlington, Iowa], is the type of the species 

 in the University of Michigan collection, and corresponds with original description 

 of the general form and proportions of the shell. This specimen, however, does 

 not preserve the suture, and the original from which the suture was described has 

 not been seen. The latter specimen was probably a fragmentary one, not preserving 

 the form of the shell, which was believed to belong to the same species as the type 

 which has been preserved. In the collection received from Prof. Calvin there is 

 a goniatite much larger than the type of G. qpii)ms, but agreeing closely with it in 

 its general form and proportions in all respects save in its relatively larger umbilicus. 

 This specimeu is illustrated on Pis. VIII and IX [in "Weller's paper cited above], 

 and it is believed to be an individual of the same species as the type of G. opiums; 

 but, unlike the type specimen, several of the sutures are fairly well preserved, and 

 ai'e entirely different from the sutures of G. opiiin"^ as indicated in the original 

 description. It is therefore probable that the suture originall}^ described as that of 

 G. opinuis is really that of some shell which is not only specifically but generically 

 distinct from G. opinius. The true suture of the species is in all respects that of 

 the genus Agoniatites, and therefore the species is placed in that genus. Heretofore 

 this genus has been recognized only in the Devonian, and in America, at least, at no 

 higher horizon than the Middle Devonian. 



Occurrence. — Lower Carboniferous, Kinderhook stage, Chonopectus 



sandstone, Burlington, Iowa. 



Family GEPHYROCERATID^. 



Genus NoMisMOCERAS Hyatt. 



This genus was established by Hyatt," with Goniatites spirorhis Phillips 

 as the type, to include evolute shells with wide umbilicus and g'lyphioceran 

 septa; it was regarded as belonging to the Glyphioceratidaj, section 

 Dimorphocera^. Haug** classes Nomismoceras under the Gephyroceratidse, 

 and regards it as the radical of the Meekoceratidte of the Trias, the series 

 being Nomismoceras, Paralecanites, Lecanites, Meekoceras. 



" Proc. Boston Soc. Nat. Hist., Vol. XXII, p. 330. * Etudes sur les Goniatites, p. 4(i. 



MOX XLII — 02 3 



