34 CATALOGUE OF 



the subject, for Prof. R. Bellini most kindly sent me specimens from 

 Poll's original locality at Caserta, of the only Pisidium there found. 

 These undoubtedly belong to the present form and show that Poli 

 was dealing with dead and bleached specimens rather rounder in 

 lateral outline than the majority of those met with. Poll's diagnosis 

 (138, i, ord. n, p. 65) is as follows : 



" Testae characters. Testa subrotunda. convexiuscula, glabra, 

 fragilissima, striis tenuissimis confertisque trans versim dis- 

 tincta. 



Testce descri.ptio. Testa subrotunda, transversim paullo 

 oblongata, tumidiuscula, exigua. Valvae glabras, maxima 

 fragiles, striis exilissimis lente conspicuis confertisque, perinde 

 ac annotinis accesionibus, exaratse conspiciuntur. Tota. concha 

 niveo candore nitet. 



Natural! 8 hujus concha3 magnitude via duas tresve lineas 

 excedit. Nos vero longe ampliorem delineavimus ad ipsam 

 clarius repnesentandam. 



Historia. Cardium hoc in rivuli alveo per regium Casertse 

 nemus pra3terfluentis simul cum aliis testis fluviatilibus 

 invenimus animante destitntum." 



IJaudon seems to have been the next, of the few who clearly 

 discriminated this species, to give a really good description (9, p. -343), 

 and since it supplies much that is wanting in Poli's it may well be 

 quoted : 



" Concha mediocris ant exigua, variabilis, ovata, vix elonga- 

 tula, parum subventricosa, antice subrostrata, posterius 

 subrotunda, inferius curvata, griseo lutescenti colore induta ; 

 margine valvulis clausis acuta ; apice vix prominente ; striis 

 tenuibus et sat regulariter distributis ; commissura angusta ; 

 arcuata; dentibus cardinalibus augustis |~siV], sublamellosis. 

 Ligamento brevi, flavo vel brunneo, debili." 



To this may now be appended a detailed description of the hinge- 

 characters : 



Hinge (PI. I, f. 3-6 ; III, f. 3) about f the length of the 

 shell, very strong and wide, projecting well inwards, very arched, 

 with two flexures in the right valve of which the anterior ono 

 is the more marked. 



R.V. a. i. about -f% the length of the hinge-line, very strong, 

 curved and inclined inwards ; base very strong, some- 

 what swollen ; apex on distal side of centre, prominent, 

 acuminate, distally directed ; ridges rounded, distal steep, 

 especially at first, umbonal fairly steep and descending 

 to a lower level than the distal. 



a. in. about | the length of, and parallel to a. /., straight, 

 narrow, erect ; apex central, prominent, rounded obtuse ; 

 ridr/es compressed, sloping away equally and riot 

 steeply. 



