220 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Among these filled cusps are included doubtless those which have 

 pa&sed through the V-bar stage as well as those which have grown by 

 gradual out-building, since from present knowledge it is impossible to 

 separate the two groups. With better maps and descriptions of the 

 cusps a later classification will make closer distinctions. 



Theory confronted loith Fact. — After this general survey of the varying 

 forms of cuspate forelands selected from the many examples in the nar- 

 row water bodies of the world, the following generalization may be 

 made. However varied the form resulting from the local conditions, 

 tides, relief of oldland, etc., the axis, or a line drawn from the point of 

 the cusp through the centre of the foreland, is always at right angles to 

 the general direction of flow of the tidal currents. 



Where there are strong tides, as in Paget sound, Chesapeake bay, and 

 Narragansett bay, there are numerous and typical cuspate forelands ; 

 while in Albemarle sound the range of tides is less than one foot, and 

 here few sandy points of a cuspate form occur. 



Thus tlie facts of observation seem to correspond with the principal 

 requirement of the theory. Studies of the existing currents in regions 

 where these forelands are found are now needed to further test the tidal 

 hypothesis. From present knowledge this seems to be the best working 

 hypothesis. 



Two methods of growth are suggested. Jn one the outline of the 

 foreland is early given by a V-bar, and later this enclosed lagoon is pro- 

 gressively filled. In the other the foreland grows by successive additions 

 to the mainland. The first appears to be by far the larger class ; though 

 the examples of the latter are liable to be confused with the filled stage 

 of the first class. 



Between the narrow channels and the open sea there are all gradations 

 in size of water bodies, so we should expect to find forelands built by 

 combination of tidal and wind currents in different proportions. Such 

 cases have been referred to in Del Faro point, Aro island cusp, and 

 Alice point. 



13. Bat-deltas. 



History of a Drowned Valley. — Bay-deltas fill drowned valleys. The 

 term ria, from the Spanish, may be advantageously used to cover all 

 types of subaerially carved troughs, including von Richthofen's fjord, ria, 

 dalmation, and liman types.* After depression, the stream in youth 



* Fiihrer, 305-312. Compare use by Pencik, Morphologie der Erdoberfliiche, 

 II. 562-582. 



