234 



CALCAREOUS MANURES— APPENDIX. 



three strata,) "considerable green-sand." Stith's, Surry, '-quite richly 

 specked with green-sand." A. C. Jones', Surry, and at Kingsmill, James City, 

 " intermixed with green-sand." Now what proportions these descriptions 

 designate, it is not for me to determine ; but 3 or 4 per cent., at most, would 

 abundantly serve to meet all their requisitions. There are also 7 other of the 

 specimens named marked in less degrees by the presence of this ingredient, 

 and which are described in this respect in such phrases as these : containing 

 " a little green-sand"—" specked with green-sand"—" quite perceptibly 

 specked with green-sand" — "tinged with green-sand"— and "slightly inter- 

 mixed with green-sand." There remain of the list 135 other specimens, 

 of which 48 are stated to contain of "green-sand a trace" (by which term 

 chemists understand a proportion so small that its presence is barely cer- 

 tain,) and of the other 87 specimens no green-sand is mentioned, and 

 therefore it may be inferred that not even "a trace" could be found. 



If this list of marls and statements of their fertilizing contents had been 

 presented by the author distinctly as a designed refutation of his previously 

 and repeatedly published opinions of the frequent abundance and general 

 presence in useful quantity of green-sand in miocene marls, nothing could 

 have been more to the purpose, or more conclusive. 



Nevertheless, few and rare as may be the cases in which the value and 

 beneficial effects of marls are increased in any considerable degree by the 

 presence of green-sand, or of any other ingredient than carbonate of lime, 

 it is important that such auxiliary fertilizing matters should be searched 

 for, and their absence or presence known. The great value and uni- 

 form fertilizing effects of carbonate of lime will be the most highly appre- 

 ciated by those farmers who understand and estimate them separately 

 and alone; without confounding the operation of that manuring earth with 

 those of any other intermixed and unknown substances, no matter what 

 increase of benefit such intermixture may produce in particular cases. 



KNOWN SHELLS OF THE MARLS OF LOWER VIRGINIA.* 



Miocene. 



Astarte undulata, Say. 



" concentrica, Conrad. 

 " vicina, Say. 

 Artemis acetabulum " 

 Area incile, Say. 

 " centenaria, Say. 

 *• limula, Con. 

 " idonea " 



Ballanus ? 



Buccinum porcinum, Say. 

 " obsoietum " 

 " laqueatum " 

 " altile, Co7i. 

 Cardium laqueatum, Con. 

 " Virginianum " 

 Chama congregata, Con. 



" corticosa, " 

 Corbula cuneata, " 

 " inequale, Say. 

 Crassatella undulata, Say. 

 Carditamera arata, Con. 

 Cardita granulata, Say. 

 Cytherea reposta, Con. 



Crepidula aculeata, Lamarck. 

 " fornicata " 



Conus ? 



Dentalium thallus, Cdh. 

 Dispotaea costata, Say. 

 Fusus quadricostatus. Say. 

 " cenereus " 



" exilis, Con. 



Fissurella, ? 



Fasciolaria mutabilis, Con. 

 Gnathodon cuneatum, Gray. 

 Isocardia rusfica, Sowcrby. 

 Lucina divaricata, Lam. 



" contracta, Say. 



" anodonta, " 



" cribaria, " 



•' squamosa, Lam. 

 Lithodendron lineatus, Con. 

 Murex umbrifer, Con. 

 Mactra delumbis, " 



Marginella ? 



Natica heros, Say. 

 " duplicata. Say. 



* I am indebted to my friend M. Tuomey for this list of the known tertiary shells in 

 my collection. There are also sundry other species or varieties which are doubtful or 

 undetermined, and therefore are not here enumerated. 



