76 TROCKKDINOS OK THE MAIACOLOGICAL SOCIKTY. 



We have considered tliis unique species of so much importance in 

 the history of the British Eocene Pulmonata, that we have ventured 

 to reproduce Mr. Edwards' original figures as well as his description 

 of both genus and species. Tlie author regarded his new genus as an 

 aberrant form of the Limmridai, and placed it between Limncea and 

 Chilina. This view, we believe, has not since been questioned, though 

 prior to liis examination it was supposed by Mr. Hickman to resemble 

 Vuluta, an erroneous determination, however, as there Avere no indica- 

 tions of the columcllar plaits so characteristic of that genus. The 

 species was discovered in some abundance in the AYoolwich Beds by 

 Mr. Hickman in 1860 (associated with fiuviatile shells, Cyrena, etc., 

 and remains of a terrestrial flora) when the South High-Level Sewer 

 was being constructed between Peckham and Dulwich. We have not 

 heard of its occurrence elsewhere in the London Basin, and as far as 

 we can testify the genus is entirely unknown in Continental areas, 

 and is not living at the present day. 



Formation. — Eocene (Woolwich Beds). Localities. — Peckham and 

 Dulwich. 



PLAXOEBIS, E. L. Geoffrey, 1767. 

 Planokbis incertus, n.sp. PI. VL Fig. 12. 



Planorhis incertus (Edwards MS.), R. B. jS'ewton. — Syst. List 

 Edwards Coll. British Museum, 1891, p. 282. 



Shell dextral, discoidal and depressed; whorls six, siib-cylindrical, 

 gradually increasing and divided by a deep suture ; umbilical area 

 wide and moderately concave ; surface ornamented with closely arranged 

 minute concentric lines, and bearing five or six e(][uidistant carina?, 

 producing obtuse angulations ; stria? of growth well defined. Diam. 9 ; 

 alt. 2'5 mm. 



This elegant little specimen is the sole example known to us. 

 It exliibits a basal surface only, the upper part of the test being 

 embedded in the surrounding matrix. The shell is fractured in 

 places, displaying the cast, on which the carinse are distinctly seen 

 encircling the whorls. These keels and the minute concentric stria3 

 serve to distinguish this species fi'om the Planorhis Sparnacensis, 

 Deshayes, which occurs in the Lower Eocene of France. The French 

 species exhibits many features in common with the English form, but 

 beyond numerous lines of growth which cover the whorls it is entirely 

 destitute of any ornamentation. 



Searles Wood described and figured a somewhat similar shell from 

 the Woolwich Beds of Dulwich', in the Mon. Pal. Soc. 1877, p. 340, 

 pi. xxxiv. fig. 1, which ho doubtfully referred to P. Icerir/atus, 

 Deshayes, but as his identification was based upon casts it is highly 

 probable that his specimen might be more correctly determined as 

 P. incertus ; however, not having seen his type, we are unable to give 

 any decided opinion regarding it. 



Formation. — Eocene (Woolwich Beds). Locality. — Peckham. 



