SPECIES OF PISIDIUM. 93 



CROMERIAN. 



NORFOLK. EAST. EN. 



West Runton [A. S. K.]. [N. M.]. 



The Continental range of this species is probably Europe north of 

 the Alps. It certainly occurs in Scandinavia [Lynge Coll.], France 

 and Transylvania [Norman Coll., B.M. 98.5.20 : 22170-83 pars & 

 22444-55 purs], Kussia [Lindholm Coll.], and has been received 

 from Lake Baikal labelled P. mucronatum. 



It has been found in the Holocene and Pleistocene of Denmark 

 [Johansen (85, p. 9)] ; in the Pleistocene (Campinien) of Brussels 

 [Mus. Hist. Nat. Brussels]. 



10. Pisidium henslowanum (Sheppard). 



[Pis. II, f. 4; III, f. 9; XXIII, f. 21-31 ; XXIV; XXV, f. 13; 

 XXVI, f. 13.] 



1825. Tellina lienslowana, Leach MS. : Sheppard, Trans. Linn. Soc. xiv, 

 p. 150 



1831. Cyclas appendiculata, Leach MS. : Turton, Manual, p. 15, f. 6. 



1832. Pisidium hensloicianum, nobis : Jenyns, Trans. Camb. Phil. Soc. 



iv, p. 308, pi. xxi, ff. 6 & 7. 

 1852. Pera appendiculata : Leach, Moll. Brit. Synop. p. 292. 



1854. Pisum henslwvianum, Shepp. : Deshayes, Cat. Conch. Brit. Mus. 



ii, p. 278. 



1855. Pisidium hensloicianum, var. nucleus (" non appendicule"e ") : id., 



torn. cit. p. 347. 



1858. Musculium hensloicianum, Shepp. : Adams, Gen. Rec. Moll, ii, 



p. 451. 



1859. Pisidium hensloioianum : Jeffreys, Ann. & Mag. Nat. Hist, in, 



iii, p. 37. 

 1862. Pisidium fontinale, var. henslowana : Jeffreys, Brit. Conch, i, 



p. 21. 

 1903. Corneocydas (Tropidocyclas) henslowianum, Shepp. : Dall, Proc. 



Biol. Soc. Washington, xvi, p. 7. 



Sheppard first received this very characteristic shell from Leach 

 under the name of Pera Jienslowana after its discoverer Prof. J. S. 

 Heuslow. Leach afterwards seems to have changed the name to 

 Ptra appendiculata, transferring the former specific designation 

 to a form of Pisidium amnicum. 



Sheppard, however, described the shell under the name he had 

 received with it as follows (163, p. 150) : 



" T. [ = Tellina] testa oblique subovata transversim vix 

 sulcata, projectura a basi umbonis adornata. 



Habitat in rivis. 



Testa 2 lin. longa [=alt.], 2| lin. lata [=long.], cornei 

 coloris, glabra, striata, vix sulcata, anterius planiuscula. 



I first received this species from Dr. Leach, and a very 

 distinct one it is .... its decisive characteristic arises from a 

 curious eave-like projection at the bases of the umbones." 



