IOWA ACADEMY OF SCIENCES. HI 



S. Jahulis, as reported, is an extreme form of S. solidulum. It should 

 be dropped from the list. 



S. partumeium, S. jayamim, and S. sj^hoerictim, as identified by Prof. 

 Witter, also from one series, and are the same species, S. splmrictwi being 

 intermediate. Our specimens are not typical S. j)arlumemni, but resemble 

 tyi>\ciil S.jayanuin more nearly. If 8. j^nrtumeium should prove to be a 

 valid species, which is doubtful, then all of our specimens (including 

 S.sphaericum as identified by Prof. Witter) must be referred to S.jayanum, 

 Prime. 



This leaves seven species of Sphaerictim in the State: S. sulcatum, Lam., 

 S. stiiatmum, Lam., S. rhomboideum. Say, S. jayamim, Prime, S. trans- 

 versum, Say. S. sec^ire. Prime, and »S. triuicatum, Lius. 



Mr. Charles R. Keyes. in the list already referred to, also reports the fol- 

 lowing additional epecies: 



Tridopsis palliata, Say. 



Ancylus tardus, Say. 



Am^nicola orbiculata. Lea. 



VARIATION IN THE SUCCINID.E OF THE LOESS. 



BY B. SHIMEK. 



The recent species of the genus Succitiea are certainly puzzling, but those 

 which are found as fossils in the loess deposits of the Missouri and Missis- 

 sippi valleys are positively bewildering. The fossil forms belong princi- 

 pally to the avara and obliqua groups, but few specimens belonging to the 

 ovalis group occurring. Without entering into a detailed discussion of the 

 various forms it may be briefly stated that an examination of the specimens, 

 both recent and fossil, which are herewith submitted, will show the follow- 

 ing facts: 



The three forms which are commonly found in the loess are S. obliqua. 

 Say, S. avara. Say S. lijieata, Binn. A careful weighing of the variation in 

 the recent specimens of these species, supplemented by the almost unbroken 

 series of fossil forms, shows that typical S. avara varied through the larger 

 form of the same species to S. obliqua in one direction, with a smaller 

 branch running into -S. lineata in another. In other words, I am convinced 

 that however dift'ereut these species may appear now, they were once the 

 same, the original stock occurring perhaps just before the loess. 



The variation in these forms, or in the original form, was not the result 

 of climatic conditions, for all forms often occur in the same deposit. 



It is expected that a more complete report on this variation, with proper 

 plates, will be elaborated in the near future. 



It may be of interest to note that our small typical fossil, .S. avara, is 

 identical with S. oblonga, Drap., from the loess of Germany. 



