46 THE NAUTILUS. 



GENEKAL NOTES. 



The following interesting notes are taken from the Journal of 

 Conchology, Vol. x, no. 2, pp. 35-42, April, 1901, " Conchology at 

 the Dawn and Close of the Nineteenth Century " (The Presidential 

 Address delivered by Mr. E. R. Sykes, at the Annual Meeting of 

 the Conchological Society of Great Britain and Ireland, Oct. 27, 

 1900). 



* * * "The close of the Nineteenth Century is, to use a com- 

 mercial expression, a time to 'take stock,' and consider what prog- 

 ress has been made. It is with one of these forms of estimating our 

 present position that I propose for a few minutes to concern myself, 

 and especially with an endeavor to arrive at some idea of the actual 

 number of species of recent mollusca which are now known to 

 science. Any such estimate can but be approximate, but a survey 

 of the most recent monographs enables one to form a fairly accurate 

 conception. 



" The classic starting-point for such a calculation, as indeed for 

 all other systematic molluscan work, is the tenth edition of Linnaeus." 

 His works contain roughly speaking about 700 species. This 

 number gradually increased nearly every year, until " Dillwyn, in 

 1817, was enabled to enumerate 2,244; which we may divide into: 

 Cephalopoda, 45; Gastropoda, 1,510; Scaphopoda, 15; Pelecypoda, 

 638 ; Polyplacophora, 36. 



In the classic work of the brothers Adams (1853-58) we find the 

 following: Cephalopoda, 197; Gastropoda, 12,604; Scaphopoda, 

 46; Pelecypoda, 4,258; Polyplacophora, 216. 



Treating Paetel's well-known work (1888-1890) in the same way 

 we get : Cephalopoda, 305 ; Gastropoda, 35,134; Scaphopoda, 1 37 ; 

 Pe/ecypoda, 8,467 ; Polyplacophora, 439 ; or a total of 44,482 

 species. 



" Hoyle's catalogue of the recent Cephalopoda in 1886, with ad- 

 denda in 1896, contains 469. From the Zoological Record of 

 1897-9, we add eleven, and on an average, we may include four for 

 1900, making a total of 484 species. 



In the Gastropoda the recent catalogue of the Cyclophoridse, Cy- 

 clostoynatidce, and allies, by Kobelt and Moellendorff, " yields about 

 2,444 species, and if we add 48 species from the Zool. Record of 

 1899, and estimate a similar number for the 1900, we get 2,541." 

 Since Paetel's list in 1888 (omitting the Gyclophoridcz, etc.), basing 

 1900 on a three years' average (682), there have been recorded 7,396, 

 a total estimate of 43,021. 



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

 Sharp, yields 238 ; if we add the single one in the record of 1899, 

 and another for 1900, we have 240 species. 



For the Pelecypoda we have since Paetel's list (1890), basing as 

 before, 1900 on a three years' average (142), 1,056; a total of 

 9,523 species. 



