712 CRETACEOUS PALEONTOLOGY. 



extended in a narrow border along the side of the beak to a 

 point opposite the base or swell of the volution, where it rapidly 

 widens out into the broad wing-like lip, which reaches somewhat 

 over the next volution above but apparently not forming a 

 posterior canal. The outer posterior angle of the expanded por- 

 tion is prolonged into a narrow, recurved, falciform process of 

 greater or less extent; volutions marked by oblique longitudinal 

 folds, which extend from suture to suture on all the upper volu- 

 tions, but become obsolete just above the middle on the body por- 

 tion of the last one, and are entirely obsolete on the back of the 

 expanded lip. On the upper volutions the folds are closely 

 arranged, but on the lower they are more distant and more 

 strongly marked, while on the body part of the last one they are 

 quite strong and almost node-like, even on many of the internal 

 casts." (Whitfield.) 



Remarks. Morton's description of this species does not agree 

 well with his illustration of the same, and as there is some doubt 

 as to the type specimen, it is not quite clear just what the species 

 is. It is altogether probable, however, that the specimens which 

 Whitfield has illustrated under this name are true representatives 

 of the species, and it will be so considered here. However, Whit- 

 field has described three other species as new, from specimens 

 which are certainly specifically identical with his examples of A. 

 pennata, these species being Anchura compressa, Rostellaria com- 

 pact and Rositellariai spirata. This species is represented by 

 numerous casts in the faunas of the Navesink marl, where it is 

 one of the commonest species of gastropods. These casts are 

 usually incomplete towards the aperture, so that the expanded 

 lip is rarely preserved, and they vary considerably in the strength 

 of the vertical nodes of the shell, many of them being essenti- 

 ally smooth, although in the shells themselves these nodes were, 

 doubtless, uniformly present. In a large series of specimens 

 certain ones may be selected which agree more closely with one 

 of Whitfield's supposed species than another, but they all run 

 together to such a degree that it is not possible to draw specific 

 lines between them. All of Whitfield's types have been studied 

 in this connection. 



