198 PROCEEDINGS OF THE AMERICAN ACADEMY. 



has evidently been no complete closing of lagoon and then a later reopening, this 

 would indicate the direction of growth, particularly when it accords with tlie evi- 

 dence from the shore curves, as it does in this case. This example then apparently 

 combines the features of single and double tombolos. 



Monastir (Tunis, 57) is built on an island tied by two tombolos. This example 

 is worthy of special field studj* to bring out the relations of the several uncom- 

 pleted tombolos, apparently built from the mainland toward the island before the 

 formation of tlie present tombolos which enclose tlie others. 



Jasmund is tied to Riigen island by two beautifully curving tombolos (Germ., 

 42,64). At Lietzow there is a third connection with the mainland across a narrow 

 portion of the enclosed lagoon, but this in part at least is artificial. Transportation 

 is indicated as slightly stronger from the right, wliile the squareness of the bar 

 suggests that it was built largely from the bottom. 



San Juan Nepomucino island, Lower California, is composed of two parts con- 

 nected by bars completely enclosing a salt lagoon (H. 0., 1223). 



Margarita island, oft the coast of Venezuela, consists of two individuals joined 

 by two bars enclosing Laguna Grande (H. 0., 374). 



Presqu'ile de Giens (Fr., 248). 



V. Lngoon-marsh-meadow (Adolescence) : Colchester Point. — After 

 formation of a lagoon by a Y-tombolo or a double tombolo, the wind 

 blows in sand from the beaches and streams, and tides deposit silt, so that 

 in time the lagoon is converted into marsh and the marsh in turn into 

 meadow, if the island is not first consumed by the continued attack 

 of the sea. 



On the Plattsburg, N. Y., sheet of the Geological Survey, at Colchester point, 

 Vermont, are two cases of filled lagoons, each having an almost extinguished pond. 

 The western pond still maintains connection witb the lake, while the eastern pond 

 has no outlet. 



The lagoon between Cumberland head and the mainland is two thirds filled, 

 Woodruff pond overflowing across the last built bar into lake Champlain (G. S., 

 Platt.sburg, N. Y.). 



" The Bonnet" on the west side of Narrangansett bay appears to be an island 

 tied to the mainland (C. S., 353). Wesquage pond is the lagoon between tlie 

 tombolos. 



Sachuest point, east of Newport (C. S., 35::!, 3044), has the lagoon between its 

 two connecting tombolos almost completely filled. 



Monte Circeo south of Home is completely tied (Ital., 170). 



Tiree island (Scot., 42) appears to be composed of two islands connected by 

 " The Reef." Further study is here needed. 



Between San Franeisquito and Santa Teresa bays, Lower California, there is a 

 low dune-covered tract connecting land 300-600 feet high with the mainland. Tlie 

 only trace of a lagoon is the bed of a pond, half a mile in diameter, which is said 

 to contain fresh water during four months of the year (H. 0., 638). 



Three islands are tied together and to the mainland west of Sacrificios island, 

 Mexico. Two of the lagoons are completely filled, and the third one is more than 

 half filled (H. 0., 875). 



