218 Miscellaneous. 



the last three are as unquestionably Eocene Tertiary. The second 

 I regard as representing a transitional epoch ; but some geologists 

 assign it to the Cretaceous period, because of the presence of dino- 

 saurian remains in its strata. Others refer it to the Tertiary, 

 because of the characteristics of its floral remains. It is sufficient 

 for my present purpose to say that the molluscan types here dis- 

 cussed are found in strata which range from the Cretaceous to the 

 close of the Eocene inclusive. 



The comprehensive genera that embrace the minor types which 

 are here more especially discussed or referred to are Limncea, Pla- 

 norbis, Physa, Helix, Papa, Succinea, and Unio. The minor types 

 that may be mentioned as having representatives among the fossil 

 collections already referred to are especially noticeable among the 

 pulnionate Gasteropoda and the Unionidae. The principal examples 

 of the former are indicated by the following list of the names by 

 which the types are known, and which have been applied to them by 

 different authors in either a generic or subgeneric sense. These 

 examples by no means represent, even approximately, the full mol- 

 luscau faunas of which they form a part ; but they are selected for 

 the special purpose already indicated. 



LlMN.EIX^E. HELICINJE. 



1. Acella, Haldeman. 9. Aglaia, Albers. 



2. Leptolimnffia, Swainson. 10. Arianta, Leach. 



3. Liinnophysa, Fitzintjer. 11. Patula, Haldeman. 



12. Strobila, Morse. 

 Planorbinje. 13. Triodopsis, Rajinesque. 



4. Planorbis (typical), Ouettard. Pupin^e 



5. Bathyomphalua Agassi*. Leucocheila, Alb. $ Mart. 



6. Gyraulus, Agassiz. ^ p ^ 



Physin.^:. -^ Holospira ?, Albers*. 



7. Physa (typical), Drapamaud. Succinic. 



8. Bulinus, Adanson. 17. Brachyspira, Pfeiffer. 



It should be mentioned that these subordinate types were origi- 

 nally recognized among, and their names applied wholly to, living 

 forms. The discovery of fossil forms of those types is a gratifying 

 confirmation of their genuineness (time being the crucial test of 

 permanency), and proof of the sagacity of their authors. 



Acella is represented by A. Haldemani, White f, from the Laramie 

 strata of Bear-River valley, Wyoming. With the probable excep- 

 tion of an undescribed form in the Green-River strata of Wyoming, 

 no other fossil species of that type is yet known ; but the Limncea 

 (Pleurolimncea) tenuicostata of Meek and Hayden, from the Laramie 

 strata of Montana, is a closely allied form. Limncea (Leptolimtum ?) 

 miauscula, White, from the Green-River strata of Wyoming, appears 



* Holospira is placed here under the Pupince only conventionally. 



t The species herein mentioned are described and in part figured in the 

 following publications : — Animal Reports U S. Geol. Surv. Terr. ; vol. ix. 

 (4to ser.) of the same ; Bulletin of the same ; Powell's Rep. Geol. Uinta 

 Mts. ; U.S. Expl. and Surv. west of the 100th Merid., vol. iv. ; U.S. 

 Geol. Surv. 40th Parallel, vol. iv. ; Simpson's Rep. Great Basin, Utah; 

 and Proc. U.S. National Museum, vol. iii. (The latter now in press.) 



