156 KANSAS UNIVERSITY SCIENCE BULLETIN. 



the Permian rocks as well, where they occur in abundance, 

 I hardly think I ever saw two of them with the same degree 

 of lobation. It is true, however, that none of them possess 

 such large lobes as those referred to by Meek and separated 

 from Eumicrotis by Hind. Nevertheless the lobation exists, 

 even in the type species of EumicroHx, to some considerable 

 extent among many individuals. To separate these out would 

 be to split a single species into two genera. However, it 

 should be remarked that the beaks are not so inflated and 

 drawn out as in some specimens of P. speluncaria as figured 

 by King. Neither are they so incurved over the hinge. But 

 this feature also is an extremely variable one in our American 

 species, and of itself is hardly of generic value. In the light 

 of these facts it seems to me advisable to retain the term 

 Pseudomonotis for the American fossils usually grouped under 

 that term. Furthermore, I believe that they are sufficiently 

 divided into species and varieties, with perhaps one exception, 

 so far as they are known to me. 



PSEUDOMONOTIS? sp. 



Plate VII, figure 1. 



Fragments of two flat valves, with very peculiar markings. 

 The outline of the lower portion of the shell is nearly cir- 

 cular ; the upper part unknown. The ribs are small and 

 slender, flexuous, and made nodose by vaulted scales. They 

 are spaced four times their diameter apart. There is occa- 

 sionally a faint trace of an intermediate striation seen in the 

 bottom of the broad, flat furrows. The whole area is crowded 

 with fine, imbricating growth marks or concentric striae. 

 The length of the larger fragment is 24 mm. 



Whitehorse spring, Oklahoma; rare. 



The flexuous, nodular striae remind one of PseudomonotiSy 

 but it may belong to some other genus. 



MYALINA sp 



Plate VI, figure 7. 



Shell rather small, quite elongate ; beak apparently pointed. 

 This specimen, the only one in the collection, has the beak 

 broken away. The angle between the hinge and the front 

 margin is about 38 or 40 degrees. The specimen is too frag- 



