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ON EANELLA LEUCOSTOMA, LAMARCK. 



Ey Edgae a. Smith, I.S.O. 



Read 9th April, 1915. 



The object of the present note is to find a permanent generic resting- 

 place ' for this well-kno-wn shell, which in the past has been shifted 

 from one genns to another, and also to raise to specific rank a form 

 from South Africa hitherto regarded as a variety of it. 



In the year 1811 it was placed in the genus Biplex by Perry; in 

 1822 Lamarck, and Deshayes in 1830, called it a Ranella; in 1833 it 

 was deemed a Triton by Quoy «& Gairaard ; in 1842, 1843, 1844, 

 1870, 1886, 1892, and 1903 it reverted to Eanella on the authority of 

 Kiener, Deshayes, lleeve, Kobelt, Sowerby, and Martens ; in 1 857 

 Gray transferred it to Apollon\ in 1853 and 1867 it reposed in Bursa 

 (sub-genus Jpollon) teste H. & A. Adams and Angas ; in 1881 and 

 1885 Tryon and Watson regarded it as a Ilanella of the sub-genus 

 Argohuccinum; in 1888, on the authority of Pritchaid & GatlifF, 

 Lotoriiim (sub-genus Argohuccinum) claimed it; in 1901 and 1902 

 Hedley and Kesteven gave it a temporary resting-place in Gyrineum; 

 in 1904 Hutton placed it in Apollo; in 1906 Smith referred it 

 to Septa, and in 1912 and 1913 Verco and Suter located it in 

 Argobuccinum. 



In deciding the proper position of this species it all depends upon 

 what characters should be regarded of generic importance. If it 

 were merely a question of selecting the oldest name applied to 

 the groups '■Triton'' and '■ Ranella\ as understood by Lamarck, tlie 

 matter would be comparatively simple, but in the present day the 

 tendency is to multiply generic divisions, and consequently there is 

 much more difficulty, in the present case at all events, of selecting 

 the right genus. 



Since Ranella leucostoma in shell chiiracters has a greater general 

 resemblance to the big 'Triton shells' (e.g. rubicunda, Perry = 

 ajistralis, Lamarck) than to any other group, and the opercula are 

 similar, I am inclined to place it along with them in the genus 

 Charonia of Gistei. Dall * at one time considered this name 

 synonymous with Septa of Perry, but it has since been pointed out 

 by Matthews & Iredale' that this was a false conclusion. Iredale * 

 subsequently clearly proved that the type of Septa of Perry is not 

 the species selected by Dall, who at the time had not consulted 

 Perry's earlier work, the Arcana, in which the first introduction of 

 Septa appeared. 



The external features of the animal of Banella leucostoma have been 

 described by Quoy & Gaimard,* and they are similar in general 



^ This is almost a hopeless task until the animals of the various groups of 



Tritons have been investigated. 

 •^ Smithsonian Misc. Coll., vol. xlviii, p. 134, 1904. 

 •' Victorian Naturalist, vol. xxix, p. 9, 1912. 

 ^ Natitilus, vol. xxvii, p. 55, 1913. 

 ^ Voy. Astrolabe, Zool., vol. ii, p. 547. 



