ii6 



ROCHESTER ACADEMY OF SCIENCE. 



[March 14, 



lamella, (/) proceeding downward from the cural process (c) following 

 the curve of the inside of the dorsal valve (d) in the Spiriferidoe, con- 

 tinuing to the front, then curvmg upward along the inside of the ven- 

 tral valve (v, fig. 7) to near the crural process — but curving outward 

 and following the same course to form a spiral coil (s.) The primary 

 lamellos of the coils of the two sides are joined by a cross-bar (/->) 

 somewhere between the points of the crura on the front extremity of 

 the primary lamellae before they begin their upward turn. (See fig- 

 ures 5, 6, 7.) 



In the Terebratulidffi, there are the same calcified lamellae (1. figs, i, 

 2, 3 and 4) from each of the crurae (c) in the same way following the 

 curve of the inside of the dorsal valve (d) toward the front (/); at 

 the front they turn backward, forming a loop (/) by folding, so that 

 the exterior surface (facing the side of the shell) of the primary 

 lamella becomes the interior face of the part which is bent upward to 

 form the loop. In the living forms there is, proceeding from the 

 backward folded end of the loop, a coil {a) of fleshy spiral aims — but 

 the direction of the coiling is the reverse of that of the spire (.f) of the 

 Spiriferidae, that is, when viewed from the side the primary coil of the 

 spire passes from the upper end of the calcified loops toward the 

 neutral valve and follows the curve of the inside of that valve towards 

 the front when it approaches the dorsal valve and curves backward 

 towards its origin. (Compare figures 4 and 7.) 



The conclusion which I felt safe in drawing, was that the spiral 



