154 KANSAS UNIVERSITY SCIENCE BULLETIN. 



species from the lower Permian of Kansas, though the char- 

 acters of the muscular scars at once distinguish it. In form 

 this species resembles the rest of the Red Beds species. Its 

 distinguishing characters are two subparallel teeth on the 

 anterior end of the hinge, the lower of which may be con- 

 nected with the buttress. Posterior adductor large. Length 

 of hinge, 5 mm. ; length of specimen, 7.5 mm. ; height at 

 posterior end, 4.5 mm. 



Whitehorse spring, Oklahoma; common. Dozier, Tex.; 

 common. 



The average umbonal angle seems to be larger and the 

 shell somewhat broader with respect to the hinge than in the 

 other species. 



It should be remarked here that the forms of these species 

 are not sufficiently well preserved to distinguish between 

 them with certainty. It is very probable that with well- 

 preserved material, showing all the critical features of each 

 species, they might be readily separated. As it is, a speci- 

 men showing the outline or surface features does not have 

 the teeth preserved, and vice versa. 



PSEUDOMONOTIS Beyrich. 



Hind^" splits the genus Pseudomonotis into two genera, sep- 

 arating F. haw7ii Meek from P. apeluncaria Schlotheim. His 

 grounds for doing so are: "This species [P. speluncaria] , 

 however, has a peculiar posterior lobe separated from the rest 

 of the valve by an oblique sinus ; the left umbo is arched to 

 a greater extent, and the hinge-line not so pronounced as in 

 Eumicrotis.'^ With these remarks the question is dismissed, 

 and Eumicrotis of Meek is given to those shells without the 

 sinus and lobe, while the others are apparently left with 

 Psetidomoii'dis and regarded as Permian. This may hold for 

 European specimens of this group, but it is very difficult of 

 application in this country. Meek's discussion of the type 

 species of his proposed genus Enmicrotus, which he after- 

 ward conceded to be synonymous with Pseudomonotis , will nof 

 be out of place here. It is as follows : ^^ 



50. Brit. Garb. Lain., 11, pt. 2, pp. 41-44, 1903. 



51. Pal. Dpp. Mo., p. 5.1, 1864. 



