14 



Atbypa. Section I. 



Without longitudinal striae, and with the edges of the 

 valves upon one plane. (" Cardinal area none.") 



ATRYPA pectinifera. 



TAB. DCXVI. 



Spec. Char. Transversely obovate ; surface covered 

 with concentric ciliated fringes. 



1 HE valves of this shell are moderately and equally con- 

 vex, the larger beak is only slightly prominent, and the 

 internal septa are obscure. 



Very abundant in the magnesian limestone of Humble- 

 ton Hill, near Sunderland. It is one of the Terebratulae 

 spoken of by Professor Sedgwick in his paper on the mag- 

 nesian limestone (Geol. Trans. New Series, Vol. III. 

 pt. I. 119), and several other shells there mentioned as 

 Terebratulas have spiral appendages, and belong also to 

 the genus Atrypa. 



The three middle figures are magnified. 



ATRYPA expansa. 



TAB. DCXYU.—Jig. 1. 



Spec. Char. Orbicular, becoming- transversely oval 

 with age, convex ; front even ; surface covered 

 with broad, striated, imbricating fringes; beak 

 small, produced, incurved. 



Syn. Spirifera expansa. Phill. Geol. Yorks. Pt. II. 

 220. P/.X/. 18. 



