CHAP. XXVIII.] HEAPS OF GNATHODON. 107 



canal. The shell road, so called from the materials used in. its 

 construction, namely, the valves of the Gnathodon cuneatus, 

 before mentioned, is of a dazzling white color, and in the bright 

 sunshine formed a strong contrast with the vegetation of the ad 

 joining swamps. Yet the verdure of the tail cypresses is some 

 what dimmed by the somber color of the gray Spanish moss hang 

 ing every where from its boughs like drapery. The rich clusters 

 of scarlet and purplish fruit of the red maple (Acer Drummondii) 

 were very conspicuous, and the willows have just unfolded their 

 apple-green leaves. The swamp palmetto ( Chamcerops adanso- 

 nia) raises its fan-shaped leaves ten feet high, although without 

 any main trunk, like the sea-island palmetto before described. 

 Several of them are surmounted by spikes bearing seeds. Among 

 the spring flowers we gathered violets ( Viola cuculata), the ele 

 gant Housto?iia serpyllifolia, which we had first seen at Clai- 

 borne, and a white bramble (Rubus, trivialis), the odor of which 

 resembles that of our primrose. The common white clover, also, 

 is most abundant here, as on the banks of the Mississippi, below 

 New Orleans ; yet it is not a native of Louisiana, and some bot 

 anists doubt whether any of the European species now growing 

 wild in this state are indigenous. 



Lake Pontchartrain is about fifteen feet below high water, and 

 two feet below the lowest water of the Mississippi. It is said to 

 have become sensibly shallower in the last forty years, its depth 

 being now fourteen or fifteen feet only, for it receives annual sup 

 plies of mud from the Mississippi, poured into it by one of its 

 mouths, called the Iberville River. 



The southeast wind sometimes drives the salt water into the 

 great lagoon, and raises its level from five to ten feet. On a mud 

 bank near the shore I observed the living Gnathodon, accom 

 panied by a modiola (JDreissena ?), and there was a small bank 

 of dead shells on the southern borders of the lake, which may 

 have been thrown up by the waves in a storm, the valves of most 

 of them being separate. I learned that the road materials before 

 spoken of were procured from the east end, where there is an 

 enormous mound of dead shells, a mile long, fifteen feet high, and 

 from twenty to sixty yards broad. Dr. Riddell, Director of the 



