1903.] NATURAL SCIEN'CES OF PHILADELPHIA. 281 



anteriorly below the middle and the aperture and canal together are 

 half as long as the shell. Outer lip wdth a plicate band parallel with 

 the edge at a short distance therefrom. Length 15.5 mm., width 

 about 6 mm. 



Me tula fragilis n. sp. 



This is apparently the direct descendant of fastkUosa in the Upper 

 Vicksburg marl and is a much larger species, with more numerous and 

 relatively much finer and more close-set ribs; it is very thin and deli- 

 cate in substance, very rare and always occurs in a fragmentary 

 condition. From a fragment before me I am able to compute 

 the diameter of the body whorl to be about 10 mm. The longitudinal 

 riblets are at least 90 in number, and the revolving lines on the largest 

 whorl of the spire about 20. No varices can be seen on the fragments 

 before me. The revolving grooves are shallow, those near the base 

 and apex of the whorls broader and more thoroughly olDliterating the 

 ribs. The ribs are broadly arcuate longitudinally. The length of 

 the specimen at hand must have been at least 25 mm. The shell walls 

 are composed of three layers, of which the inner, very thin, and the 

 outer, thicker, are solid and amorphous in texture, the two separated 

 by a very thin layer of prismatic structure having the fibres perpen- 

 dicular to the surface. 



Olivella affluens n. sp. 



There are two yery distinct species of Olivella occurring abund- 

 antly in the \'icksburg strata. One of these, which may be assumed 

 to be the typical 7nississippiensis , has the nucleus small, of very few 

 whorls and the nucleal sutures obhterated. The whorls of the spire are 

 completely unexcavated along the anterior edge. . The other species 

 named as above, is as common as mississippiensis; it is rather smaller, 

 the nucleus being, however, much larger, very obtuse, composed of 

 about three whorls having the sutures all distinct and impressed. Each 

 whorl of the spire has a deep and clearly defined revolving groove at 

 the lower margin, which is entirely wanting in mississippiensis. The 

 anterior folds of the columella are less oblique than in that species. 

 Length of a moderately large specimen, having four body whorls beside 

 the nucleus, 14.5 mm., width 5.7 mm. The aperture is somewhat nar- 

 row, and is rather less than two-thirds the total length of the shell. 

 The differences between these two species are at least subgeneric. 



It would seem to me that Fulgur spiniger and nochdatum, of Conrad, 

 are distinct species and not mere varieties of one. I have collected a 

 number of specimens of spiniger, and there is no marked variability 



