112 JOURNAL OF CONCHOI.OGY, VOL. l6, NO. 4, AUGUST, I92O. 



with the Balea, they present no feature calling for special remark. 

 Bouchard-Chantereaux, in addition to the present series, enumerates 

 Clausilia bidens \^C. laminata\ C. solida, C. plicatula, C. parviila, 

 and C. ventricosa. 



Zua lubrica (Miill). — Represented by var. lubricoides Fer., found 

 at Audruicq in July, and later on the banks of the lagoon, Calais. 

 Bouchard-Chantereaux, under the name of Bidiiniis hibricus, speaks 

 of it as very common. 



Succinea elegans Risso is represented from two localities. 

 Characteristic specimens of var. sarsii Esm., var. cotitortula Baudon 

 and var. longiscata Morelet are present in gatherings from the canal 

 banks at Audruicq in June, and m. scalariforine, a very interesting, fine 

 clean shell, was found in May by a pond at Polincove. Bouchard- 

 Chantereaux does not appear to have found this species unless it is 

 confused with his Siiccmea a^nphibia. 



Succinea putris (L.). — A single specimen from the canal banks 

 at Audruicq, representative of var. fitzgeraldiana Hazay. Bouchard- 

 Chantereaux alludes to this species under the name of S. amphibia as 

 very common and variable, and in addition enumerates S. ob/o/iga and 

 S. arenaria. 



Carychium minimum Miill. — Locally common, from Polincove. 

 It is an obese form referable to the var. ovata Bourguignat. Bouchard- 

 Chantereaux records it as very common. 



The Aquatic Gastropods number twenty-two species and several 

 show a noticeable and unusual tendency to form a . thick, white, 

 calcareous margin to the apertures, which is remarkable in a 

 district said to be totally devoid of limestone. 



Segmentina lineata(Walker). — Surprisinglyabundant and widely 

 distributed, and represented from Ht^nuin and Polincove. Specimens 

 gathered in November from a ditch at Hdnuin are very fine, some 

 being almost eight mm. in diameter, the var. major Pascal ; most of 

 these are very glossy, and show as many as four internal septa very 

 distinctly, as well as a clear white sutural line, which is probably due 

 to a calcareous deposit. 



Shells from Polincove collected during September are smaller, with 

 feebly developed septa and show no trace of the sutural line. Re- 

 corded by Bouchard-Chantereaux as Planorbis jiitidus Miill. The 

 septa are found in quite young individuals, and vary in number and 

 development in the adult. Jeffreys was in error in stating that the 

 septa were only present in mature shells, they exist from a very early 

 stage and are progressively absorbed as the shell is enlarged. 



