SPECIES OF PISIDU'M. 101 



Schmidt's original description (156, p. 119) is as follows : 



" Vorder- und Hinterseite des Oberrandes stossen in den 

 Wirbeln recht-, ja selbst spitzwinklig zusammen ; auf den 

 "VVirbelnbefindet sicli eine scharfe llunzel; das kurze Ligament 

 springt deutlichvor; Schlosszahne uuverhiiltnissmassig dick; 

 dabei i&t die kleine Muschel so bauchig und der Vorderrund 

 so weit vorgestrcckt, dass sie sich gern auf das Vorderende des 

 lUickenslegt und den scharfeii TJnterrand emporkehrt deshalb 

 nenne ich sie Pis. tupinum." 



He adds a little later that the appendiculse on the umbones are 

 not always present. 



Uaudon's diagnosis (9, p. 362) being yet clearer we append it : 



" Concha triaugularis, obliqua, alta, convexa ad umbones, 

 solida, subopaca, tenuiter stria ta, supcrius couica, interims 

 arcuata, antice rostrata, postice vix subcurvata, pallida, corneo 

 lutea vel flavesceris ; apicibus subacutis lamella superatis ; 

 ligamento brevi, lineari, flavido ; commissura crassissima, 

 praesertim quoquoversus et undique crenulata ; duobus dentibus 

 cardinalibus, tuberculosis, vix conspicuis." 



He has, however, mistaken the characters of the hinge-teeth, the 

 details of which are as under : 



Hinge (PI. II, f. 5 ; IV, f. 7) nearly | the length of the shell, 

 massive, projecting well inwards, strongly arched with two 

 flexures. 



H.V. a. I. about 1 the length of the hinge-line, very stout, curving 

 sharply inwards ; base exceedingly deep, solid and 

 swollen ; apex near distal end, moderately prominent, 

 rounded obtuse ; ridges very round, sloping about 

 equally and fairly steeply. 



. ///. about the length of a. ]., from which it is separated by 

 a deep fossa ; somewhat apposed to the shell-margin : 

 apex on distal side of centre, not very prominent : 

 ridges rounded, distal short and steep, umboual longer 

 and less steep. 



3. scarcely prominent, narrow, arcuate ; a nearly parallel 

 to the shell-margin, b curving diagonally to the inner 

 margin of the hinge-plate. 



>). I. length about \ that of hinge-line, very strong, narrow, 

 slightly curving inwards ; base strong, swollen ; apex 

 distal side of centre, scarcely prominent, very obtusely 

 acuminate ; ridges not much rounded, umbonal long 

 and gradually sloping, distal short, at tirst nearly 

 vertical, then sloping gently. 



p. in. not quite | the length of p. /., narrow, somewuat 

 apposed to the shell-margin ; apex near distal end ; 



