12 CATAT.OGTE OF 



wis a tube marked " Pisidium pmillum large variety J. G. 

 Jeff." (PI. XIII, f. 2; XV, f. 12) containing typical 

 P. casertanum.* 



1882. When the first volume of Jeffreys' " British Conchology " 

 appeared he still recognized five species of Pisi'lium, but the 

 collocation of the forms was not quite the same. The 

 new arrangement was as follows : 



m . , f 1. P. (imnicum. 



A. inangular < /. .. 7 



[ 2. P. fonttnale. 



B. OvaJ. 3. P.psillum. 



C. Hound. 4. P. nitidum. 



D. Oblong. 5. P. roseum. 



The change was that Jeffreys no longer considered 

 P. fonttnale to be a variety of P. pusillum, but reckoned it 

 a distinct species, pnttinti under it as varieties P. Jienslowi- 

 anum, P. pulcliellum, and P. cinereum. 



With the substitution of the name P. milium for P. roseum 

 this arrangement has persisted down to quite recent times 

 in the history of British Conchology. 



1863. lieeve, whose work (147) has not altogether received the 



attention it merits, raised the number of species to seven 

 by according specific rank to P. obtusale, P. pulcltellum, and 

 P. hznsloivwnuin, whilst leaving P. milium, as represented 

 by some of its many names, under the synonymy of 

 P. pulchMum. 



1864. E. von Martens (108) described, under the name of 



P. anliffuum, a form from the Pleistocene of Siberia, that 

 was subsequently redescribed in 1880 by Sandborger from 

 the Cromerian of West liunton as P. astartoides. This form 

 had long been reckoned merely a variety of P. <imnicum. 

 Von Martens' name being preoccupied, Sandberger's stands 

 for the species. 



1874-77. Clessin wrote that portion of his Monograph on the 

 Cycladea (35) which deals with Pisidium. 



He advocated the employment of the hinge-characters in 

 the discrimination of the species, of which he admitted far 

 more than British authors would, although by no means so 

 lavish of them as some continental writers. He was 

 badly served by his printer, for the work abounds in typo- 

 graphical errors, and by his artist, for, with the exception 

 of P. milium, the coloured figures are distorted travesties 

 and the diagrams of the hinge-teeth incorrect. 



1886. Cle.sin (59) named P. Klljeborgii, a form recently met with 

 in Ireland. 



1S1U. Westerlund (185) added an Irish species, P. hibernicum, to 

 the British List. 



* Jenyns, si? alre;idy noted (nnle, p. 1(M. was inclined to refer Alder's 

 P. cinereum to his own 7'. pusilltiiH. 



