828 ANNUAL OF SCIENTIFIC DISCOVERY. 



distribution. From the Arctic, Gulf-stream, and African currents, 

 the modification of the zones of temperature in the Atlantic is very 

 striking. For instance, the temperate zone on the American side ex- 

 tends only from Cape Hatteras to Cape Cod, about ten degrees of 

 latitude, while on the European it extends from the coast of Sweden 

 to the Cape de Verd Islands, nearly five times as many degrees. On 

 the contrary, the tropical zone, which extends in America from Cape 

 Hatteras to 25 S. latitude, or sixty degrees, extends only about 

 twenty degrees on the African Guinea coast. The line of tempera- 

 ture established by the average of the thirty coldest days in the year 

 gives the clue to the distribution of the marine fauna ; in America 

 this is essentially tropical, and in Europe essentially temperate. 



Of the families mentioned in this list, the Cottoids are essentially 

 North American, and there are five in Jamaica ; the Scicenoids are 

 tropical, Europe having but a few ; the Sparoids are essentially 

 Mediterranean, where fifteen genera exist, and there are four in 

 Jamaica ; the Squammipennce are tropical, and numerous in Jamaica ; 

 the Scomberoids are cosmopolitan, and numerous everywhere ; the 

 Mullets are tropical, and there are several in Jamaica ; the Labroids, 

 very rare here, are numerous in the tropics ; the Cyprinoids, though 

 quite cosmopolitan, have never been found in South America, and 

 there are none in Jamaica ; one Centropomus is found in fresh water 

 in Jamaica, which is unusual; the Siluroids are few, and those of 

 America few in comparison with those of Asia; while a kindred 

 family, the Goniodonts, are peculiar to this country ; the Pleuronec- 

 tidce belong to the temperate zone, yet there are few here. 



J. M. Barnard, Esq., stated a fact in confirmation of the tropical 

 character of the American marine fauna : he had lately received a 

 keg of echinoderms from Zanzibar, in 5 S. latitude, which were al- 

 most identical with those from East Florida. 



CUEIOTIS FACTS IN RELATION TO THE COD. 



At a recent meeting of the Boston Nat. Hist. Soc., Capt. Atwood 

 stated that fish are often swallowed by the cod, pass from their stom- 

 ach into the abdominal cavity, and are there found "mummified" 

 and adherent to the inner walls ; he presented a specimen, apparently 

 of the eel family, thus preserved and hardened, which he had taken 

 from the abdominal cavity of a pollock. Cod are often so wounded 

 by the hooks that the intestines hang out in the water, and yet such 

 fish are seen swimming about with the rest without apparent suffer-,, 

 ing, and he had no doubt that they bite at the hooks in a few days. 

 Ho presented two large cod hooks, with portions of the line attached, 

 which he had taken from the livers of apparently healthy cod. The 

 greater part of the hooks was buried in the organ, and must have re- 

 mained there, he thought, at least twelve months ; they must have 

 been swallowed, broken off, and have worked their way through the 

 stomach into the liver. 



RATE OF INCREASE OF FRESH-WATER SHELLS. 



At a recent meeting of the Boston Society of Natural History, 



