34 CATALOGUE OF 



the subject, for Prof. 11. Bellini most kindly sent me specimens from 

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

 These undoubtedly belong to the present form and show that Poli 

 \vas dealing with dead and bleached specimens rather rounder in 

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

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



" Testa; charactfres. Testa subrotunda, convcxiuscula, glabra, 

 fragilissima, striis tenuissimis confertisque transversim dis- 

 tincta. 



Testa; descriptio. Testa subrotunda, transversim paullo 

 oblongata, tumidiuscula, exigua. Valvae glabras, maxime 

 fragiles, striis exilissimis lente conspicuis confertisque, perinde 

 ac annotinis accesionibus, exaratee conspiciuntur. Tota concha 

 niveo candore nitet. 



Naturalis hujus concha3 magnitude via duas tresve lineas 

 excedit. Nos vero longe ampliorem delineavimus ad ipsam 

 clarius repraesentandam. 



Historia. Cardium hoc in rivuli alveo per regiutn Casertae 

 nemus praatorflucntis simnl cum aliis testis fluviatilibus 

 invenimus animante destitutum." 



Baudon 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 aut 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 |".V], sublamellotas. 

 Ligamento brevi, flavo vel brunneo, dcbili." 



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

 characters : 



Hiwje (PI. I, f. 3-6; 111, f. 3) about | 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. 



ll.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 ; ridyes rounded, distal steep, 

 especially at first, umbonal fairly steep and descending 

 to a lower level than the distal. 



a. ni. about ^ the length of, and parallel to a. f., straight, 

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

 ridges compressed, sloping away equally and not 

 steeply. 



