HELIX. 85 



minates in an acute angle at the centre of the aperture ; beneath 

 exhibiting only two volutions, of which the external one is slightly 

 grooved near the suture. 



Inhabits Alabama. Breadth, one fourth of an inch. Cabinet of 

 the Academy. 



This species is about the same size as P. avara, but, besides 

 other characters, it is sufficiently distinguished by the acute fold of 

 the labrum. It was sent to the Academy by Mr. Samuel Hazard. 



A more careful study has induced me to change my 

 opinion of the identity of this species with H. Troostiana. 



Bland is the only author who has correctly dealt with 

 this species. His description is given below, while his 

 figure is given on pi. 78, fig. 13. He proposed this name 

 in place of Say's preoccupied one. 



This shell may be distinguished from fatigiata Say, and Troos- 

 tiana Lea, independently of the absence of the carina, by its smaller 

 size, and more particularly by the different form, relative size, and 

 position of the teeth. In those species the superior tooth on the 

 peristome is transverse, compressed, and larger than the inferior 

 one, from which it is separated by a " remarkable sinus," distinctly 

 visible on looking into the aperture ; the inferior tooth is obtuse. 

 Immediately behind the peristome, the position of the teeth is 

 marked by small shallow pits, giving the character to the last 

 whorl designated by Shuttleworth " scrohiculato-constrictus" — the 

 striae run over the whorl up to the peristome. In H. Hazardi, the 

 two teeth on the peristome are of the same character as the supe- 

 rior one in fatigiata and Troostiana, — the inferior tooth is how- 

 ever the largest, and so partially conceals the lower margin of the 

 superior one as to obstruct the view into the aperture, and give no 

 appearance of separation "by a remarkable sinus." Both the teeth 

 are more deeply seated than in the other species. The nature of 

 the scrobiculation behind the peristome in H Hazardi alone suffi- 

 ciently distinguishes it from its allies. The space behind the peris- 

 tome, and between it and the curved pit, showing the seat of the 

 superior tooth, is convex and smooth, the strise not extending over it. 



This species has, in common with fatigiata Say and Troostiana 



