Contributions to Invertebrate Palaeontology. 561 



Genus ORTHIS Dalmaii. 



Ortliis tioga. 



Plate XIII, fig. 3. 



Orthis tioga Hall, Pal. N. Y., vol. 4, p. 59, pi. 8, figs. 20-29. 



Among the concretionary nodules of the Erie shale from Leroj, 

 Lake Co., there is one which contains impressions, or casts, of 

 several valves of the above-named species. The specimens are 

 somewhat smaller than the general run of the New York Chemung 

 specimens, but otherwise cannot be distinguished from them. The 

 most entire ones are dorsal valves, and are moderately convex, with 

 a decided mesial sinus. The form is transversly oval or elliptical, 

 with a short cardinal area and small depressed beak ; the striae are 

 rather coarse, frequently bifurcated and much recurved on the car- 

 dinal margins and slopes, many of them running off on the cardi- 

 nal border. Muscular scars large and sub-flabellate, all the features 

 being the same as the typical forms of the species, modified only in 



size. 



4 



Genus PAL^EOl^EILO H. and W. 



Preliminary Notice of Lamellib. Shells of the Upper Held., Hamilton and Che- 

 mung groups, etc., N. Y. State Cab. Nat. Hist., Dec. 1869, p. 6. 



Palaeoneilo siiuilis. 



Plate XII, figs. 4 and 5. 



Palaeoneilo simills "Whitf., Ann. N. Y. Acad. Sci., 1882, p. 217. 



Shell oblong, with nearly equally rounded extremities, and almost parallel 

 dorsal and ventral margins. Anterior end short, a little narrower tlian the 

 body of the shell, resiilting from the constriction below the beaks. Posterior 

 end rounded, with a slight oblique truncation below the middle of the height, 

 corresponding to the very shallow umbonal sulcus of the valves. Beaks situ- 

 ated'within the anterior third of the length of the shell, small and enrolled. 

 Valves ventricose, most prominent just below the umbones, and slightly sul- 

 cated along the posterior slope. The surface of the shell, so far as can be de- 

 termined from the matrix, has been smooth or without visible markings. On 

 the internal cast, the condition in which the specimens are found, the muscu- 

 lar imprints are faintly marked — the pedal muscles being the most distinct. 



The species is closely related to P. (Leda) Barrisi White and 

 Whitf., Proc. Bost. Soc. Nat. Hist., vol. 8, p. 298 {Palseoneilo 

 Barrisi (W. and W.), H. & W., Prelim. Notice of Lam. Shells 



