34 PALAEONTOLOGY OF KENTUCKY. 



Brugmere. 

 Bruguiere. Encycl. Meth. 1792. Etymology : lingula, a little tongue. 



Shell oblong, compressed, sub-equivalve, attached by a pedicle passing out 

 between the valves. Shell structure minutely tubular, texture horny. Shell 

 slightly gaping at each end, truncated in front, rather pointed at the um- 

 bones ; dorsal valve rather shorter, with a thickened hinge-margin and a raised 

 central ridge inside. (Woodward.) 



Lingula triangulata. n. sp . 



Plate XXVI., Figure 1. 



Shell of medium size ; sub-triangular or broadly sub-ovate. The lateral 

 margins form, at the apex, an angle of about sixty degrees ; the sides slope 

 from apex to two-thirds of the length of shell in a straight line ; from there 

 they curve gently to basal margin, which is broadly rounded. Shell is mod- 

 erately convex from beak down to front, but depressed almost flat at margins. 

 The greatest width is about one-third of length of shell from the front ; width 

 is smaller than length. The specimen before me measures twelve lines in 

 length by ten lines in width. Shell itself is thick. The surface is marked by 

 fine concentric lines of growth, and also by fine radiating striae, both of which 

 are somewhat obscure on account of exfoliated condition of fossils, which are 

 mostly internal casts. It appears to have some resemblance with Lingula 

 paliformis of the Hamilton group, but differs from it by its shape and sur- 

 face-markings. 



Formation and Locality. Found in the Hydraulic limestone of the Devonian formation at the Falls 

 of the Ohio, in Kentucky. 



GenUS OrtMS. Dalman. 



Orthis, Dalman. Kongl. Vet. Acad. Handl. 1817. 



Etymology: Orthis, straight, in allusion to the straight hinge line. 



Shell variable in shape, sub- circular or quadrate ; valves equally or unequally 

 convex, socket valve sometimes slightly concave, with or without a mesial fold 

 or sinus ; hinge line straight, generally shorter than width of shell. Both 

 valves furnished with an area, divided by an open, triangular fissure for pas- 

 sage of the pedicle. Beaks more or less incurved, that of larger valve gener- 

 ally more produced. Surface smooth, striated, or ornamented by single, 

 bifurcated, or intercalated ribs. Structure minutely or largely punctate. 

 Valves articulating by means of teeth and sockets. 



