182 



MEDITEERANEAN PROVINCE. 



papillosum. Among the Gasteropoda, Ceritliium 

 vulgatum and C. lima are most abundant. Trochus 

 crenulatus, T. Sprattii, Rissoa ventricosa, oblonga, 

 Marginella clandestina ; Pleurotoma, four species ; 

 Natica olla ; JPhasianella, three species ; JVassa, six 

 species ; and Mitra obsoleta. The Stony Coral 

 {Garyophyllia cyathus) commences in this zone, and 

 ranges down through all succeeding ones. 



The Bivalves are fifty; twenty-two have their 

 maximum. 



The Univalves are seventy-six, sixty-two have 

 their maximum. 



The Third Region reaches from ten to twenty 

 fathoms, with a sea-bed of gravel or sand ; the 

 same plants are continued, but become scarcer to- 

 wards the lower limits of the region ; a change has 

 become obvious at depths of 160 feet, but the upper 

 limit is not so distinct or definite. The Testacea, 

 also, are to a very great extent the same. 



The Bivalves of this zone are fifty, of which 

 seventeen have their maximum here. 



The Univalves are under seventy, and twenty-six 

 are at the maximum here. 



Bivalves predominate numerically. 



The Fourth Region extends from depths of twenty 

 to thirty-five fathoms. Here, a great part of the 

 species of the upper zones are replaced by others, 

 which are curiously representative of them in form. 

 This takes place in still lower regions. There is no 

 transmutation of one into the other ; each has all 



