LAMELLIBRANCHIATA. 6l3 



This species bears some general resemblance to the fossil referred to Solemya 

 vetusta, especially in the fold of the shell on the upper anterior margin, and it 

 may prove congeneric with that form. 



Formation and locality. In the cherty layers above the Hydraulic limestone, 

 near Louisville, Ky. 



Clinopistha tellinifokmis. 



PLATE M, FIGS. 28-31. 

 Dystactella teUiniformis, U.KU.. Pal. N. Y., vol. v, pt. 1. Plates ami Explanations : PI. 51, figs. 28-31. 1888. 



Shell large, obovate ; length less than twice the height. Basal margin gently 

 curved, nearly straight anterior to the middle. Posterior end large and 

 rounded. Cardinal line arcuate. Anterior end produced, nasute, obliquely 

 truncate above. 



Valves gibbous in the middle and umbonal region. 



Beaks behind the anterior third, not prominent. Umbonal slope rounded, 

 not defined. Umbo flattened in the middle and the flattening continued 

 vertically to the base. On the anterior end there is a distinct angular ridge 

 on each valve, extending from the beaks to the antero-inferior extremity. 



Surface marked by fine striae of growth very obscurely preserved in the 

 specimens described, which are casts of the interior. Interior unknown. 



A large specimen has a length of 65 mm. and a height of about 38 mm. 

 An imperfect specimen has a height of 35 mm., a length anterior to the beaks 

 of 30 mm., and the depth of both valves is 26 mm. A small individual 

 measures 38 mm. in length, 20 mm. in height, and the depth of both valves 

 is 18 mm. 



This shell is much larger than the preceding species, the anterior end is more 

 produced, and the valves are more gibbous. 



Formation and locality. In the limestone of the Upper Helderberg group, 

 Cayuga, Ontario. 



