SYKES : CONCHOLOGY AT DAWN AND CLOSE OF NINETEENTH CENTURY. 



41 



Mcellendorff, yields about 2,445 species, and if we add forty-eight 

 species from the Zoological Record of 1899, and estimate a similar 

 number for the year 1900, we get 2,54 r. The other Gastropoda as 

 listed by Paetcl are 33,084 in number. From the Zoological Record 

 we get (omitting Cydop/ioridce, etc., as above mentioned) : — 



Therefore, estimating in this manner, we arrive at a total of 43,021 

 Gastropoda. 



As to the Scaphopods, the most recent monograph, by Pilsbry and 

 Sharp, yields 238 species ; if we add the single one in the Record of 

 1899 ^"d another for 1900, we have 240 species. 



For the Pelecypoda we have, from Paetel, 8,467. The Zoological 

 Record yields : — 



1891 

 1892 



1893 

 1894 



189.5 

 1896 



107 



57 

 62 



91 



87 

 82 



1897 149 



1898 156 



T899 ... ::. 123 



1900 (aver, of 3 yrs.) 142 

 1,056 



The grand total then becomes 9,523. 



Finally, we turn to the Anip/iineura. Here from Mr. Pilsbry's work 

 we get : Polyplacophora, 540 ; Aplacophora, 33. Adding from the 

 Zoological Record in a precisely similar manner we have to include 

 Folyplacophora, 59 ; Aplacophora, 4; and we get a final total of 636. 



The next question which arises is, how far are the above totals trust- 

 worthy ? On the one hand they are inflated by a mass of synonyms 

 which still masquerade as species, while on the other hand they are 

 reduced by a certain number of omissions. The only omission of any 

 importance, however, will, I think, be found in the Nudibranchiata, of 

 which the true total is, owing to the nature of the works consulted, 

 unduly curtailed. 



Making a reduction, therefore, for synonyms and allowing for the 

 above, I think a very fair approximation will be : — 



Cephalopoda., 450 ; Gastropoda., 40,000 ; Scaphopoda, 220 ; Pelecy- 

 poda, 8,500; Amphitieura, 600; or a grand total of 49,770 — say 

 50,000 known species of recent moUusca. 



When we consider that the known forms at the beginning of the 

 century were probably under 2,000, we get some faint idea of the 



