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POPULAR SCIENCE MONTHLY. 



Now, when the Helices of California, Mexico and a part of those 

 of the West Indies were examined, it was found that they have the dart 

 apparatus, agreeing with species of Japan, China and the Philippines, 

 not with those of Europe or of eastern North America ; for, to empha- 

 size this resemblance, the Helices of the middle and eastern United 

 States are anatomically totally unlike the Californian, Mexican and 

 Antillean, having no dart-sack or mucous gland. 



We are, therefore, confronted with a group of snails inhabiting 

 both borders of the greatest ocean, but agreeing so closely in anatomy 

 that no hypothesis but that of a common origin, descent from com- 

 mon ancestors, is conceivable. Our American dart-bearing Helices 

 must surely look to distant shores in far-off times for their ancestry. 



In the South the Oriental and Occidental members of the great 

 group of dart-bearers are separated by the breadth of the Pacific, 

 the islands of which are barren of related snails. In the North they 

 are parted by many miles of barren coast; for in America the dart- 

 bearers go no further north than Sitka, and in Asia they are not 

 known much to the northward of the Japanese Empire. 



Map showing distribution of Dart-bearing Helices in Vertical Lines. Cretaceous 

 Sea in Broken Horizontal Lines. Being on Mercator's Projection, the North- 

 ern Ranges of the Dart-bearers in America and Asia appear much 



MORE separated THAN THEY REALLY ARE. 



We know, however, that in Upper Cretaceous times the Arctic 

 lands were not, as now, clad in the scanty green of mosses, lichens 

 and herbs, with few deciduous trees, except stunted willows and the 

 like, but they bore noble forests of magnolia, beech and birch, with 

 red-woods and pines — such forests as snails love and thrive in, doubtless 



