Weno and Pawpaw Formations 77 



is separated from the second row by a sharply excavated spiral groove 

 of only half the width of the space separating the first two rows. Finally, 

 the small tubercles of the fourth row are paired with the tubercles of 

 the third row, the tubercles of a pair being connected by an obsolete radial 

 ridge. 



The angularity of the volutions is caused by the lateral projection of 

 the first and second rows of tubercles. In the type individual, the sec- 

 tion of the last volution (pi. 3, fig. 7) is elliptical in its basal (dorsal) 

 half, and the inner margin is evenly rounded. The superolateral margin 

 is incised between the three prominent tubercles, and the superior margin 

 in the region of the fourth line of small tubercles is almost straight. 



SUTURE: The type individual shows a series of suture stages be- 

 ginning on the earliest preserved volution. This volution is rounded and 



I .* o/ Q 



1 o2 , * 



Fig. 5. Turrilites bosquensis n. sp., sutures of type individual, camera lucida draw- 

 ing, x 8. The numbers indicate the volutions on which the corresponding 

 sutures occur. 



is totally smooth and tubercles begin to appear only at a diameter of 

 spiral of 2.8 mm. At this point the volution is 1.1 mm. thick and the 

 first and second rows of tubercles appear simultaneously. The suture 

 is simple and consists of a low, undissected siphonal lobe, a simple first 

 lateral saddle, a slightly smaHer and still undissected first lateral lobe, 

 a slightly bifid but otherwise simple second saddle, and an undivided 



