OF CONCHOLOGY. 203 



It was of necessity impossible that Mr. Cuming could have 

 ascertained the depth at which the shells lived that he obtained 

 from the various collections he selected from, or from other 

 dealers*. 



Though, in the vast majority of cases, the shells more recent- 

 ly named are to be regarded as the type specimens of the species 

 described and figured from Mr. Cuming's collection, unfortunate- 

 ly, from Mr. Cuming's habit of replacing shells in his cabinet 

 by better specimens when they occurred, there is a certain 

 amount of uncertainty as to these shells being the types of the 

 species described, the accuracy of the determination resting in 

 such cases on the accuracy of Mr. Cuming's determination of 

 their identity with the shells replaced; but there is no doubt that 

 in the distinction of species and varieties Mr. Cuming was very 

 acute and is to be generally depended upon. 



There is also another source of uncertainty. Mr. Cuming 

 was in the habit of sending to Dr. Pfeiffer, Reeve, SoAverby and 

 other descfibers and figurers of the species, certain specimens 

 from his duplicates marked with the same number as that attach- 

 ed to his own specimens ; and the determination of the species 

 depended on the accuracy with which these numbers were re- 

 ported. I have observed a few undoubted mistakes arising from 

 this system, and therefore believe that there may be others, 

 though probably the number is not large ; but these show the 

 necessity of depending in all these cases on the shell named 

 agreeing with the description, rather than on the fact that the 

 specimens are so named in the collection. 



A very large number of species in the collection have been 

 separated on very slight characters, or on the slightest variation 



* Indeed, I am not willing to pay so much regard to the depth at which 

 species are said to have been obtained as some geologists appear to do, 

 except when the specimens are obtained at some special dredging. My 

 faith was shaken by the following fact : — A collection of shells was offer- 

 ed to me for sale, at the time that geologists were interested in the depth 

 at which mollusca live, which I carefully examined ; but as it contained 

 many duplicates I declined it, and it was purchased by a respectable 

 dealer. And what was my astonishment, when the collection was offered 

 to me to select from, to find that each species was marked with the depth 

 at which it was obtained, for which there was not the slightest authority; 

 but the subject of depth was exciting interest at the time, and its being 

 attached to the specimen was supposed to give them an additional value ; 

 and I regret to say I have seen these pretended depths quoted in a geolo- 

 gical work as if they were true. Persons who have theories to propose 

 or support are often not sufficiently alive to the great necessity ot ex- 

 amining the authority of the statements which they receive and quote as 

 facts, or the readiness with which persons, when money is to be made 

 by the subject, are willing to stretch a point to suit their purpose. 



