JOURNAL 



OF THE 



ROYAL MICROSCOPICAL SOCIETY. 



JUNE 1888. 



TRANSACTIONS OF THE SOCIETY. 



VI. — A Revision of the Genus Aulacodiscus Ehro. 

 By John Rattray, M.A., B.Sc, F.R.S.E. 



{Read Uth March, 1888.) 

 Plates V., VI., and VII. 



In the preparation of the following monograph I have examined the 

 extensive series of specimens in the British Museum, Natural History, 

 which are included in the collections of Greville, Dickie^ W. Smith, 



EXPLANATION OF PLATES V., VI., and VII. 

 Plate V. 

 Fig. 1. — Aulacodiscus gracilis sp. n. x 660. 

 „ 2. — A. attenuatus sp. n. x 460. 

 „ - 3. — A. lucid us sp. n. x 460. 

 „ 4. — A. concinnus Kittou BIS. x 660. 

 „ 5. — A. promiueus Kitton MS. x 660. 

 „ 6. — A. inturnescens sp. n. x 460. 

 „ 7. — A. carruthersianus Kittou and Grove MS. x 460. 

 „ 8. — A. compactus sp. n. X 460. 

 „ 9. — A. dispersus sp. n. x 660. 

 „ 10. — A. rotulus sp. n. x 460. 



Plate VI. 



„ 1. — A. neglectus sp. n. x 460. 



„ 2. — A. patens sp. n. x 460. 



„ 3. — A. rnargaritaceus var. inconspicua nov. x 460. 



„ 4. — A. excavatus var. apiculata nov. x 660. 



„ 5. — A. Comberi var. irregularis uov. x 660. 



„ 6. — A. decorus var. canadensis nov. x 460. 



„ 7. — A. exiguus var. undulata nov. x 660. 



„ 8. — A. crux var. subsquamosa Grim. MS. X 660. 



„ 9. — A. umbonatus var. dirupta Grove and Sturt MS. X 660. 



Plate VII. 

 „ 1. — A. Petersii var. expansa nov. x 660. 

 „ 2. — A. Petersii var. rara nov. x 660. 

 „ 3. — A. inflatus vor. stellata nov. X 660. 

 „ 4. — A. inflatus var. minor nov. X 660. 

 „ 5. — A. amcemis var. subdecora nov. x 660. 

 „ 6. — A. spectabilis var. depressa nov. x 660. 

 „ 7. — A. Comberi Arnott x 660. Showing the inner apiculate 

 layer of the valve. 



Note. — As the new species A. parvulus milii, A. acutns mihi, and A. coronatus 

 Grove MS. came to my knowledge only after the plates were in proof, it has not been 

 possible to give figures of thein. — J. R. 



1888. 2 b 



