112 PALEONTOLOGY OF KENTUCKY. 



Spirifera davisi. N. sr. 



Plate XII., figures 1, 2, 3 and 4. 



This shell was given to me by one of the collectors around the Falls of the 

 Ohio as a Spirifera raricosta, with which it has some similarity, but from which 

 it is easily distinguished by its form and surface-markings. 



The shell is semi-circular or sub-quadrate and gibbous. Hinge-line equal or 

 larger than the greatest width of the shell. Cardinal extremities acute and 

 mostly somewhat acuminate. Surface strongly plicated. 



Ventral valve considerably more gibbous than dorsal valve, regularly arcuate 

 from beak to front ; greatest convexity at or a little above middle, and curving 

 gently to the sides and front, except at the cardinal angles, which are some- 

 what flattened ; beak much elevated above that of the opposite valve, and 

 arching over that fissure, but scarcely incurved. Cardinal area high and con- 

 cave, and reaching to the cardinal extremities. Mesial sinus is broad and 

 rounded and reaches quite to the apex. Dorsal valve gibbous, most convex in 

 the middle, flattened or a little concave towards the cardinal extremities. The 

 mesial fold is very prominent, rounded, and regularly arcuate ; it has a faint 

 impression extending from beak to middle of valve. 



The beak is small and arched over the linear area. Surface is marked by six 

 to eight rounded or sub-angular plications on each side of the mesial fold and 

 sinus. The shell is smooth, with the exception of front part, which is marked 

 by from live to seven strong concentric imbricating lines of growth, which 

 reach to the cardinal angles, and which give to the shell its peculiar beautiful 

 front view. Such imbricated front is only noticed in Spir. gregaria and in 

 Spir. mucronata, in both of which it is less regular and less prominent. Inte- 

 rior of shell is unknown. The specimens so far found show a great similarity 

 in form and also in size ; they measure from one inch to one inch and a quarter 

 in width, by from three-fourths to seven- eighths of an inch in length. This 

 species is related to Spir. raricosta and to Spir. gregaria. From the former it 

 differs in its greater number of plications; its somewhat acuminate cardinal 

 extremities ; its larger and more elevated hinge-area, and by its peculiar 

 imbricated front. From Spir. gregaria it is distinguished by its larger size, 

 by its smooth shell, by its greater width, and by its less prominent umbo, 

 and also by its more marked imbricated front. 



Formation and Locality. Spirifera davisi is found associated with Spir. gregaria in the upper 

 strata of the Devonian limestone in Kentucky and Indiana, in the neighborhood of the Falls of the Ohio; 

 it is not abundant, and only found in a few limited localities, where it occurs in well preserved specimens 

 I have named this species in honor of my friend and co-laborer, W. I. Davis, the author of " Kentucky 

 Fossil Corals," who devoted his attention and study mostly to the fossil corals, in which the Falls of the 

 Ohio and its surrounding quarries are so exceedingly rich. 



