150 Trans. Acad. Set. of St. Louis. 



subsutural lyra, two others similar to the subsutural and moderately 

 approximate at the middle and another similar lyra between the lower- 

 most of the median and the lyra forming the lower margin; spiral 

 space below the subsutural lyra exactly equal to the space between 

 the lowermost of the median lyrae and the one next below the latter. 

 Length of a specimen of about 9 body whorls, 15.5 mm.; width, 3.9 

 mm. Lisbon bed, Alabama — Mr. Aldrich strigosa n. sp. 



8trigosa is represented before me by a single specimen in 

 rather imperfect condition, but it is a very distinct species 

 readily recognizable by the characters of the table. The 

 spire whorls are more inflated in exiinia than in either stri- 

 gosa or texana, being arcuate in profile; the sides in those 

 species are nearly straight. 



Hemisurcula n. gen. 



In this genus the shell is fusiform, with the embryo con- 

 oidal, multispiral and closely coiled, the nepionic spire whorls 

 alone costate and having also an elevated collar below the 

 suture. The more recent whorls become devoid of lyrae or 

 costae, though having throughout densely close-set and sub- 

 equal microscopic striae, except the body whorl abruptly 

 below the posterior end of the aperture, which is obliquely and 

 rather coarsely lyrate. The canal is moderate, straight, and, 

 together with the aperture, forms about half the length of 

 the shell. The sinus is broadly rounded and median in 

 position on the spire whorls, the columella simple. The type 

 of this genus is PL silicata^ of Aldrich, a very remarkable 

 and isolated species occurring in the Lignitic Eocene of the 

 Gregg's Landing beds of Alabama. The beaded subsutural 

 collar, subjacent depression and swollen and finely ribbed 

 lower parts of the two whorls immediately below the embryo 

 are lost completely on the larger whorls, though the 

 subsutural collar can be feebly traced as a slightly tumid 

 line gradually descending further below the suture with 

 the growth of the shell. Besides silicata, the genus will 

 include the much stouter PL roscoei Harris, from the same 

 horizon. 



