494 



HYATT'S REVISION OP THE 



APPKoxiMAT^ ATEKAGE TEMPERATURES.. ^f Januarj of 68°, was traced by Dana^ only 



ME.VX OF MAXISItJ.M AND MIXI.IinjI. n m nt iii- 



as tar as Cape Carnaveral, but, as this table 

 shows, it probably begins again on the west 

 side, at or near Punta Rossa, and bending 

 northwards probably includes nearly the whole 

 area of the Gulf of Mexico. The whole of 

 the region favorable for the production of 

 the commercial qualities, lies between St. 

 Marks, on the coast of Florida, with an 

 isotherm for January of G3.5, and the equa- 

 torial isotherm for January of 80° ; south of 

 this equatorial isotherm, however, the limits 

 have not been ascertained, the data, both as 

 regards the sponges themselves and the tem- 

 perature, being deficient. Altho\igli the non- 

 marketable varieties occur at several places 

 in the northern zone, such as Vera Cruz, 

 Cuba, and so on, the finer sorts are only 

 found along the west coast of Florida, among 

 the Keys, and in the insular waters of the 

 Bahama and Carribean Islands. Their absence 

 from a large part of the shores of the Gulf 

 may be attributed to the sandy or soft charac- 

 ter of the coast, to the effect of the silt of the 

 Mississippi and to the absence of outlying 

 islands. The al)sence of the commercial kinds 

 from the Atlantic shore may be explained in 

 a similar manner by the frequently open and 

 sandy or clayey character of the entire coast 

 northward to New York, which would effectually prevent their existing even in the most 

 sheltered bays and nooks. Besides this the aerial isotherm of January does not represent 

 the unfavorable conditions of the climate, since at long intervals very severe winters occur 

 as far south as Chesapeake Bay, when the surface water must become very much chilled by 

 the large amount of ice formed in the numerous smaller bays, rivers and harbors, north of 

 Cape Hatteras. The severest test of the ability of the Spongiaj to withstand the climate 

 would therefore be shown by the average of the minimum or isochryme of the water for 

 January, for several successive years, taken near shore, which must necessarily be very 

 mucli below that of the average temperature or marine isotherm for that month at even a 

 short distance from the Atlantic coast, on account of the inshore or return cold current 

 from the north, A\hich prevents the influence of the warm waters of the Gulf Stream from 

 reacliiug the surface waters of the coast. That the coarser varieties of the commercial 

 sponges can survive even these adverse conditions to a certain extent, is shown Ijy the 

 specimens of Sp. agaricma, sub-species corlosia, var. divisa from Stono Inlet, South 

 Carolina. 



'These were taken on the hottom, at depths varying - Corals and Coral Islands. Kew York, 1872. 



from seven to twenty feet, according to the station. 



