88 PROCEEDINGS OF THE ACADEMY OF [1889. 



The synonymy is as follows : 



Hydrobia monroensis Frauenfeld, Verh. der k. k. zool-bot Gesell. 

 Wien, 1863, p. 1023. 



Bythinella monroensis (Frau.) Tryon, Continuation of Haldeman's 

 Monog. Fresh-water univalve Moll. U. S., p. 48. 



Not B. monroensis Dall, Proc. U. S. Nat. Mus. viii, 1885, p. 256, 

 pi. xvii, fig. 9. 



Figures 18 and 19 of the plate are drawn from specimens collected 

 by Mr. C. T. Simpson in Hillsborough River, W. Florida. I have 

 also seen specimens from Florida Springs, Fla. 

 Amnicola peracuta Pilsbry & Walker. PI. Ill fig. 20. 



Shell ovate-conoidal, rather thin, narrowly perforate, light oliv- 

 aceous or a little tinged with yellowish, quite smooth, somewhat 

 shining. Whorls about 5, or a trifle less, convex, the sutures well- 

 impressed. The spire is rather slender, acute at the apex. Aperture 

 about one-half the total leno-th of the shell or a little less, ovate, 

 angular above, broadly rounded beneath ; peristome adnate to the 

 whorl above the umbilicus. 



Alt, 4, diam 2.8 mill. 



Spivey's Lake, Navarro Co., Texas. 



This species is most nearly allied to A. cincinnatiensis Anth.. but 

 is smaller, more slender, more narrowly perforate, the whorls, es- 

 pecially the last, less convex, more sloping above. The spire of 

 A. peracuta is longer, the jieristome is adherent to the body-whorl 

 for a greater distance, and is not thickened within. The peculiar 

 dentition of A. cincinnatiensis is shared by this species. 



The types were collected by Mr. G. C. Heron, and sent me by 

 Mr. Bryant Walker of Detroit. Mich., under the above mss. name. 

 I have received the same shell from Comal Co., collected by Mr. 

 Singley. 

 Spheerium (Limosina) singley i Pilsbry. PI. Ill, figs. 14, 15. 



This is a small species allied to S. meridionale, S. maculatum, S. 

 cubense, etc. The shell is small, inequilateral, wide and truncate 

 posteriorly, narrower and rounded anteriorly, ventral margin gently 

 curved, the hinge line curved a little less than the lower outline ; 

 beaks small, not calyculate. Surface shining, striatulate. Color cor- 

 neous yellow, variegated with large and small irregular maculations 

 of blackish-brown. The blotches seem to be composed of close clusters 

 of dots. 



Length 5, alt. (at the beaks) Si, diam. 2 mill. 



