300 The American Geologist. May, 1904. 
broad, shallow mesial sinus, which is occupied bv eight (six 
to ten) sub-angular plications that interlock in front with those 
of the opposite valve. There are also from eight to ten (six 
to t-cvelve ) similar plications on each side of the sinus. Dorsal 
(Brachial) valve sharply depressed at the sides, nearly flat 
from the beak to the front, which is elevated into a broad mesial 
fold on which there are about eight (live to eleven) elevated 
plications that interlock with those of the opposite valve and 
about the same number on each side of the mesial fold." 
Shell structure: The internal laminae of the shell are highly 
punctate, with the superficial layer fibrous impunctate. 
Measurements: The average dimensions of ten examples of 
this species in our collection are as follows — Length, 13 mm.; 
breadth, 16 mm. ; thickness, 12 mm. ; width of sinus, at front, 9 
mm. ; width of plications, 0.7 mm. 
So far as we are aware, tliis species has been found only at the 
locality that yielded the type specimens ; In the Coal Measures, near 
Peoria, Peoria County, Illinois. Illinois State Museum, No. 2537. Gre- 
ger collection No. 1009. 
With our ])rescnt knowledge, the following species can, with 
certainty, be referred to the genus Rhyiichopora, — 
Rhyncliopora geiiiitsiana de Verneuil. 
RhyncJiopora nit^itini Tschernyschew. 
Rhyncliopora variabilis Stuckenberg. 
RJiyttchopora yaungi Davidson. 
Rhyiichopora thcohaldi Waagen. 
Rhyiichopora pnstiilosa White. 
Rliyncliopora illinoisensis Worthen. 
Rhyiichopora bcechert, sp. nov. 
The internal structural features exemplified in a series of 
casts of R. pustulosa and R. beeclieri and in sections of R. 
illinoisensis evince no characters at variance with the genus 
Caniarotoechia. In the brachial valve a well developed median 
septum extends somewhat forward of the transverse line and in 
the pedicle valve the dental plates arc high, prominent and cor- 
respond with the median septum in their forward extension. 
Consequently the taxonomic value of the genus as now under- 
stood rests wholly upon the punctate structure of the shell 
References. 
(i) King, W.— Ann. and Mag. of Nat. His"- 2nd. Sen. Vol. XVII. 
p. 596, pi. XII, figs, 7-1 1. 
