1486 



CRUSTACEA. 



several regions, and with regard to which the observations are free 

 from doubt; and we have confined the list to the Acephalous molluscs 

 as these appear to be sufficient to test the law under discussion. The 

 depth is given in fathoms. 



It should be observed, that to carry out the theory, the species 

 should be confined to shallower waters to the north than to the south. 





North Scot- 



South Eng- 







Malta and 



Algiers 

 and 





land and 



land and I. 



Vigo Bay. 



Gibraltar. 



jEgean. Pantel- 





Shetland. 



of Man. 









laria. 



Tunis. 



Corbula nucleus, . . 



3-80 



5-50 



6-25 



8-20 



7-80 



6-50 



8-35 



Neaera cuspidata, . . 



10-80 



50 



20 



45* 



12-185 







Tbracia phaseolina, . 



0-80? 



3-30 







7-30 







Solen pellucid us, . , 



7-100 



5-50 



.... 



' 40 







35 



Psammobia ferroensis, 



3-90 



5-50 



. 



8* 



20-40' 





10 



Tellina donacina, . . 



1-80 



5-40 







7-45 





10 



Mactra subtruncata, . 



0-12 



0-20? 



5-ib ' 









6 



Lutraria elliptica, . . 



0-10 



0-20 



Low water. 











Cytherea chione, . . 



.... 



10-20? 



. . . . 



8 



' 7-10" 



6-ll5 





Venus oyata, .... 



5-100 



7-50 



8 



6-40 



29-135 



6-40 



' 6-^35 



Venus fasciata, . . . 



5-90 



7-50 



8 



8 



27-40 



6-50 



6-35 



Venus verrucosa, . . 



.... 



0-10 



5 



6 



2-40 



6-15 



6 



Artemis lincta, . . . 



0-80 



5-50 



Low water. 



6 





6-15 



6-8 



Cardium ecbinatum, . 



5-100 



5-50 



Littoral. 





' 7-50 







Lucina flexuosa, . . 



3-100 



5-50 



4 





7-11 







Lucina spinifera, . . 



10-100 



15-30? 



10-12 



' 15-25 * 



4-30 



6-40* 



8S • 



Kellia suborbicularis, 



0-90 



10-40 



8 





29-45 35-50 





Modiola tulipa, . . . 



10-50 



5-25 



12 



' 10-25 



2-50 





35' 



Modiola, barbata, . . 



. . . . 



2-15 



«... 



. . 



7-95 



6-15' 



6-8 



Area tetragona, . . . 



10-60 



20-30 



8* 



SO 



20-80 35-50 



35 



Arcalactea, .... 





10-50 



. . . 



12-20 



0-150 





6-35 



Pectunculus glycerimis, 



5-80 



5-50 



8-12 



30 



6-24 





35 



Nucula nitida, . , . 



5-60 



5-30 



20-25 



12-40 





6-45* 



6-8 



Nucula nucleus, . . 



5-100 



5-50 



5-25 



6-20 



' 2-lo" 



6-40 



6-35 



Lima subauriculata, . 



4-100 



15-30 





35 



15-30 





35 



Pecten similis, . . . 



2-80 



20-50 



' 20*' 





27-185 





35 



Pecten maxim us, . . 



2-40 



10-30 



8 



4-2*5 



. . . 35-50 



6-8 



Pecten opercularis, 



2-100 



5-50 



8-20 



20-40 



10-70 





35 



Pecten varius, . . . 



3-20 



3-30 



8 



8 



7-55 



6-15' 



35 



Anomia epbippium, . 



0-80 



0-50 



10 | 





20-40 35-50 



6-35 



To compare fairly this table, it should be noted that the dredging 

 at the Shetlands, Orkneys, and north of Scotland, was carried to a 

 greater depth than about Southern England, fifty fathoms being the 

 limit in the latter region, as the waters are shallow. Making this 

 allowance, we are still struck with the great depth to which the species 

 penetrate at the most northern locality, instead of the small depth. 

 Out of the twenty-one species which are here mentioned as occurring 

 on Northern Scotland, or the Shetlands, and the iEgean, fourteen or 

 fifteen descend to a greater depth in the former than in the latter; and 

 nearly all the species common to the north and south extremities of 

 the British Islands, are reported from the deepest waters at the north. 

 Of the observations made at Vigo Bay, Malta, Pantellaria, Tunis, 

 Algiers, and Gibraltar, there is but a single example among the above 

 species of a greater range in depth than occurs in the northernmost 

 locality examined. The dredging in the Mediterranean by MacAn- 

 drew, was not carried to as great depths; yet even allowing for this, 



* Not found living at the depth stated. 



