40 JOUKNAL Ot" CONCliOi.OGY, VOL. lO, >fO. 2, Al'RlL, I^OI. 



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

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

 638 ; Polyplacophora, 36. It may, perhaps, be of interest to note the 

 genera with the numbers admitted in each : — Chiton, 36; Pholas, 11 ; 

 My a, 38; Tellina, 81; Cardium, 46; Macira, 38; Donax, 21 ; Venus, 

 113; Spondylus, 3; Ch.ima, 25; Area, 45; Ostrea, 83; Anomia, 30; 

 Mytilus^ 48 ; Pinna, 20 ; Argonanta, 9 ; Nautilus, 36 ; Conus, 160 ; 

 Cyprmi, 70; Bulla, 60; Valuta, 188; Buccinum, 158; Strovibus, j^t,; 

 Murex, 164; Trochus, 128; Turbo, 163; Helix, 191 ; Nerita, 65; 

 Haliotis, 17 ; Patella, 103 ; Dentaliuni, 15 ; Teredo, 4. 



Attention may be called to the large proportion of marine as com- 

 pared with land forms, and to the fact that over sixty years had only 

 resulted in the addition of 1,500 species to the lists. After this date 

 systematic and descriptive work continued with increased energy, and 

 within forty years the number had become swollen by over 15,000. 



The brothers Adams' (1853-1858) in their classic work admitted the 

 following: — Octopoda, 66; Decapoda, 125; Polypoda, 6 ; Pteropods, 

 75; Pectinibranchiata, 5,954; Scutibranchiata, 1,634; Chitons, 216; 

 Tectibranchiata, 319; Nudibranchiata, 311; Heteropoda, 70; Inoper- 

 culata, T),']^6 ; Operculata, 850; Pholadacea, 418; Veneracea, 1,883; 

 Lucinacea, 1,236; Pectinacea, 721. 



Applying the same principles to these totals we arrive at : — Cephalo- 

 poda, 197; Gastropoda, 12,604; Scaphopoda, /^6 ; Pelecypoda, 4,258; 

 Polyplacophora, 216. It should, however, be borne in mind that many 

 of their names were, and even now are, nonina nuda. 



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

 get := — Cephalopoda, T^o^ ; Pteropoda, 119; Heteropoda, 65; Gastropoda, 

 34,950; Scaphopoda, 137; Polyplacophora, 439; Pelecypoda, 8,467. 

 Dividing them in the generally recognized manner, we arrive at : — 

 Cephalopoda, 305; Gastropoda, 35,134; Scaphopoda, 137; Pelecypoda, 

 8,467 ; Polyplacophora, 439; or a total of 44,482 species. 



The next question with which we are confronted is to determine 

 wliat addenda we should make for the period which has elapsed since 

 this work was compiled, so as to bring the totals up-to-date for the 

 close of the year 1900. 



Dealing firstly with the Cephalopoda, the most complete recent cata- 

 logue is that of Hoyle in 1886, with his addenda included, so as to 

 bring the list to the close of 1896. From these we get a total of 

 469. From the Zoological Records of 1897-9, we add eleven, and, on 

 an average, we may include four for 1900 ; we therefore estimate the 

 known Cephalopoda at 484. 



Next, turning to the Gastropoda, the most recent catalogue of the 

 Cyclophoridce, Cyclostoniatidce, and allies, namely that of Kobelt and 



I All the following figures are arrived at by actual enumeration. 



