1892.] MICEOSCOPICAL JOURNAL. 2o5 



do not 3et see how it would be possible. A continued exposure 

 to low temperature would probably retard the growth of the 

 animals ; whether a point could be found where the diatoms 

 could grow and their enemies could not is uncertain, but the fact 

 of the rapid growth of diatoms in early spring makes it seem 

 probable. 



Of the fossil deposit of diatomaceous cla}- underlying the Mor- 

 ris Creek marshes I have been able to make only a superficial ex- 

 amination, as there has been no excavation except ditches, and it 

 is all under water at high tide. The ditches have brought up 

 clay from about four feet in depth ; this contains many of the 

 forms specified in article No. i, but has abundance of Navicula 

 of many varieties ; Amphora and Scoliopleura in variety are also 

 abundant. 



Boring for material in these marshes is unsatisfactorv for a 

 reason given in a former article — that is, the very unequal distri- 

 bution of the diatoms; many borings might be made inclose 

 vicinity to a rich deposit without finding it. Excavation is the 

 only satisfactory method. This the tidal waters forbid to ordi- 

 nary explorers, but the railroads cross some of these marshes, 

 and by taking advantage of their work something can be done. 

 The Shore Line railroad has lately been changing its track across 

 some of these marshes to a point nearer the shore, and has 

 brought up the deposit from greater depths than the ditches had 

 previously done. At Leete's Island I find an exceedingly inter- 

 esting deposit containing many rare and beautiful kinds. The 

 broad channel which once separated Leete's Island from the main- 

 land has been completely filled by a marine deposit, and is now 

 a salt marsh, through the eastern part of which flows Leete's Isl- 

 and Creek. This marine deposit is at least thirty feet thick and 

 is stratified ; contiguous strata of an inch or two in thickness con- 

 tain entirely difl'erent forms. 



Tropical forms abound ; several diflerent strata contain Isthmia 

 nervosa, though as I have previously mentioned finding this form 

 in the recent tnud of Boston harbor, as well as various places on 

 the Connecticut shore, it might be looked for here. The beautiful 

 Surirella Febigerii is a tropical form , but is found along the Connecti- 

 cut shore. A stratum about seven feet below the surface contains 

 this form in extraordinary abundance, the finest specimens I have 

 ever seen ; an average slide containing over fifty ; also Coscino- 

 discus, large and small, in profusion; Rhabdonema Adriaticum, 

 Tropidoneis seriata, Pleurosigma Balticum, PI. affine, all in 

 abundance ; Biddulphia, large and small varieties ; Navicula lyra, 

 N. maculata, N. Smithii, N. permagna, and numerous smaller 

 varieties ; Amphitetras antediluviana, Actinocyclus crassus, Au- 

 liscus, Raphoneis. Actinoptychus, Scoliopleura, and numerous 

 others. 



Navicula maculata is rare ; I have found it in noticeable quan- 

 tity in only one deposit previously : that was sent me from New- 



