Haynes: Fauna of the UrPER Devonian in Montana. 41 



height 35 mm., and convexity 28 mm. The largest specimen obtained 

 has a height of 47 mm., a width of 42 mm., and a convexity of 47 mm. 

 This specimen has a ratio of width to height of .89 : i, and a convexity 

 equal to the height. The cardinal view of all of the specimens is 

 sub-semicircular in outline. 



Valve of pedicle gibbous at the umbo, flattened toward the sides, 

 and deeply sinuate toward the front. Beak small, acute, and closely 

 incurved over the umbo and brachial valve. Two low, rounded pli- 

 cations and three broad furrows are present in the sinus, which is 

 scarcely defined at the umbo, but becomes broad and fairly deep at 

 the anterior margin. 



Brachial valve ventricose, with a well-defined low fold, consisting 

 of three rather broadly rounded plications, the one in the middle 

 somewhat narrower than the other two. 



Surface of both valves marked by fine concentric lines, with more 

 prominent uneven growth-wrinkles at increasingly frequent intervals 

 toward the margin of the valves. The sides of the shell show distinct 

 radiating striations, about four to one millimeter, and there are faint 

 indications of them on the sinus and on a part of the fold. 



This form is considered to be a variety of Leiorhynchus ufahense 

 Kindle, of the Jefferson limestone of Utah, from which it difi'ers in its 

 sub-semicircular and not sub-trigonal outline, and in its larger size, 

 and lesser number of plications in the sinus and fold. The type is in 

 the Carnegie Museum. 



It differs from Leiorhynchus greeneanum (Ulrich) in its greater height 

 in relation to its width; in having a sub-hemispherical rather than a 

 sub-trigonal cardinal view, and in having the fold clearly marked to 

 the anterior extremity of the valve, and containing three distinct 

 plications, instead of two or three irregular, faint plications. 



Leiorhynchus greeneanum is a younger form, and occurs in the 

 Keokuk limestone of Indiana. 



Locality. — Specimens of this new variety were collected from the 

 base of limestone number 4, and the top of green shale number 5, 

 chiefly from Three Forks and Logan. Dr. Raymond collected three 

 specimens in 1905 and the writer collected six in 1912 and ten in 1913. 



13. Leiorhynchus jeffersonense sp. nov. (Plate VIII, fig. 9.) 

 Shell large, sub-ovate and moderately convex on the brachial side; 

 flattened on the pedicle side. Width of an average specimen 44 mm.; 



