452 Trans. Acad. Sci. of St. Louis. 



even more nearly the aspect of J\f. hamiltonae than specimens 

 of M. sulcatus from Glen Park. 



SCHIZODUS APPKE8SUS (Con.)- 

 Plate 2, figs. 10-11. 



Nuculites appressa Con., Jour. Acad. Nat, Sci. Phil., vol. 8, p. 248, pL 

 15, flg. 4, (1842); Schizodus appressus RslU, Prelim. Notice Lamell., 

 2, p. 95, (1870); Schizodus Cayuga Hall., Prelim. Notice Lamell., 

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

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

 pressus Hall, Pal. N. Y., vol. 5, pt. 1, plates and explan., pi. 75, figs. 

 3-9, (1883); Schizodus appressus Hall, Pal. N. Y., vol. 6, pt. 1, p. 449^ 

 pi. 75, figs. 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 illustratioub of S. appressua fails to reveal charac- 

 ters sufficiently 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 so 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 S. 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 Waver ly, under the name S. prolongatus.^ 



MODIOMORPHA LAMELLOSA U. Sp. 



Plate 2, figs. 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. 5, pt. 453, pi. 75, figs. 37-40, 45. 

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



