512 S. WELLER MISSISSIPPIAN RHYNCHONELLIFORM SHELLS 



PUGNOIDES N. GEN. 

 PUGNOIDES OTTUMWA (WHITE) 



One of the rhynchonelloid shells which has been commonly referred by 

 recent authors to the genus Pugnax is Rhynchonella ottumwa White. A 

 series of cross-sections of this species is reproduced in figure 131, in which 

 it is shown to possess all the essential internal characters of Camarotoechia. 

 If, however, it is legitimate to recognize such genera as Wilsonia and 

 Leioi^liynchus, genera possessing essentially the same internal structure as 



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Figure 13. — Cross-sections of the rostral Portion of Pugnoides ottximxoa {White) 



This series of eleven cross-sections (X -%) is from a specimen from tlie Telia beds of 



Iowa 



Camarotoechia, and based primarily upon the external form and orna- 

 mentation of the shell, then R. ottumwa, with its external aspect of Pug- 

 nax, must also be excluded from Camarotoechia, and as there is no genus 

 in which it can be placed, it becomes necessary to establish a new one for 

 its reception. This genus may be called Pugnoides, with P. ottumiua as 

 genotype. 



Shitmardella n. gen. 



bhumardella mi880urien8is (shumard) 



A species of rhynchonelliform shell from the Chouteau limestone was 

 described by Shumard in 1855 as Rhynchonella missouriensis. The con- 

 tour and ornamentation of the shell is peculiar, and it has commonly 

 been referred to the genus Pugnax by recent authors, evidently because 

 of its coarse plications, which become more or less obsolescent toward the 

 beak. The presence of a strong median septum in the brachial valve, 

 however, must exclude the specie's from that genus, and the internal 

 characters of the shell are so different from other species that, associated 

 as they are with the peculiar external forn , the species may be taken as 

 the type of a new genus, Shumardella. A series of cross-sections of the 

 shell is shown in figure 14. In this genus the median septum of the 

 brachial valve is divided internally by a narrov/ median incision, which, 

 however, is not open cardinally to f^^^^m an open crural cavity as in 

 Camarotoechia, but is arched over, as . •lo'wn in figure 14^. The me- 



