308 Mr Jenyns's Monograph on the 



There can scarcely be a doubt that this is the minute shell found 

 by Montagu (Test. Brit. 88.) which he confounded with the young of 

 P. amnicum. Mr Alder sent me a small variety of it from Newcastle 

 as his Cyclas fontinalis, and I do not feel certain that it is not the 

 Pisidium fontinale of Pfeiffer whose characters in some respects accord 

 better with this species than with P. pusillum already described. 



My largest specimens of this shell are from the neighbourhood of 

 Battersea Fields. 



Sp. 5. P. Henslowianum, Nobis.— Tab. xxi. Fig. 6, 7. 



P. testa oblique ovali, ventricosa, tenuiter striata; umbonibus sub- 

 acutis, projectura lamelliformi adornatis. 



Long. 2^ lin. Alt. 2 lin. Crass. If lin. 

 Pera Henslowiana, Leach (olim.) 



Tellina Henslowiana, Shepp. in Linn. Trans. 14. 150. 

 Pera appendiculata, Leach MSS. in Brit. Mat. 

 Cyclas appendiculata, Turt. Man. 15. f. 6. 

 Animal album, tubo siphonali brevi, quoad formam paulo variabili; ple- 



rumque subconico, apice truncate. 

 Testa oblique ovalis, ventricosa, antice planiuscula, distinete inaequilate- 

 ralis, tenuiter striata, nitide lutescenti-alba, vel cornea, saepius partim 

 prsecipue ad apicem, sorde ferruginea obtecta: umbohes acutiusculi. 

 projectura parva lamelliformi adornatis. 



Obs. In pullis projectura medio valvularum insidet ; hinc gradatim 

 assurgit, acerescente testa.— (Vide Fig. 8, 9-) 



The discovery of this very peculiar and well marked species is like- 

 wise due to Professor Henslow, who first found it in ditches com- 

 municating with the river Cam in the immediate neighbourhood of, and 

 also a few miles below Cambridge. Dr Leach named it after him : 



