452 Trans. Acad. Set. of St. Louis. 



even more nearly the aspect of M. hamiltonae than apecimens 

 of M. sulcatui from Glen Park. 



SOHIZODUS APPRESSDS (Con.)- 

 PlaU2,fig». 10-11. 



Nuculites appreata Con., Joar. Acad. Nat. Sci. Pbll., vol. 8, p. 248, pi. 

 15, fig. 4, (1842); Schizodua appreasua R&M, FreVim. Notice Lamell., 

 2, p. J>5, (1870); Schizodua Cayuga Hall., Prelim. Notice Lamell., 

 2, p. 95, (1870); Cytherodon appreaaut Hall, 23rd Rep. N. Y. St. Mos. 

 Nat. Hist., expl. pi. 14, fig. 20, (1872); Cytherodon (^SchiModua) ap- 

 preaaua Hall, Pal. N. Y., vol. 5, pt. 1, plates and explan., pi. 76, figs. 

 8-9, (1883); Schizodus appreaaua Hall, Pal. N. Y., vol. 5, pt. 1, p. 449, 

 pi. 75, flgs. 3-9, (1885). 



This is one of the less common species of pelecypods in the 

 Glen Park fauna. A careful comparison of the specimens 

 with Halls illustratioDb of S. appressus fails to reveal charac- 

 ters suflBciently marked to allow it to be separated from that 

 species of the Hamilton fauna in New York State. The Glen 

 Park specimens, perhaps, have the beak slightly more ante- 

 rior in position with the anterior marginal slope from the beak 

 a little more abrupt, and none of the Glen Park specimens 

 attain qo large a size as the larger ones of the New York 

 specimens. 



Another allied species is 8. chemungensis (Con.), of the 

 New York Chemung fauna,* which is probably genetically 

 related to 8. appressus of the preceding Hamilton fauna. 

 The Glen Park specimens, however, resemble the Hamilton 

 shell much more closely than they do the Chemung species. 

 Herrick has described another closely related species from the 

 Ohio Waverly, under the name 8. prolongatus.^ 



MODIOMORPHA LAMELLOSA n. Sp. 



Plate 2, figa. 12-13. 



Description. Shell equivalved, rather small for the genus, 

 obliquely subovate in outline, widest posteriorly, width one- 

 half or a little more than one-half the length, beaks small, 

 subangular, flattened, directed forward, nearly terminal. 

 Dorsal margin arcuate, curving into the posterior margin 



• Pal. N. Y., vol. 6, pt. 468, pi. 76, flgs. 37-40, 45. 



t Bull. Sci. Lab. Den. Univ., vol. 4, p. 36, pi. 6, flg. 1. 



