46 THE AMEEICAN MONTHLY [February, 



twenty feet above tbe bottom of tbe deposit. What the strata 

 below this contains I haA'e not yet found out, but hope to do so 

 hereafter. 



On the north side of the island the marsh widens out into 

 what was once a broad bay, and extends northward for some 

 miles; under all this marsh lies the diatomaceous clay. Much 

 of this clay is by no means rich, but all contains some diatoms, 

 not a single ounce that I have examined but what would vield 

 diatoms enough for many dozen of slides. Since my previous 

 article was written I have partially explored Leete's Island 

 creek. I find it, like Morris and Stony creeks, rich in P. 

 ame7'icanum. In a ditch flowing into this creek I find Pleni'o- 

 sig'ma tcrryanuin with Naviciila maciilata^ both in such 

 abundance that they may be easily separated from other forms, 

 and form by themselves a nearly pure gathering; with them 

 appear also an abundance of Navicida perinagna of a peculiar 

 type, and large specimens of Nitzschia scalaris. 



This I consider a choice find. I have never heard of any- 

 thing like it elsewhere, and I think all the Leete's island slides 

 specially interesting. I have lately examined the upper stratum 

 from different points, and find it extraordinarily rich in Navlcjila 

 didymiis and other types of N. constricta ^ and also the different 

 types of N. eUiptica. 



West of the depot a new track has been laid through the marsh, 

 and in building bridges and culverts a considerable amount of 

 the deposithasbeen thrown up ; this contains the same Coscinodis- 

 cus^ Actinopiychiis^ Amphora^ Rhabdonetna^ JVavicula, Scolio- 

 pleura^ Orthosira^ Surh-clla febegerii^ with a larger amount 

 of Actinocyclus crassns^ Auliscus sculptiis^ Campylodiscus 

 eche?ieis, etc. Of recent material I found, in one gathering 

 from a ditch near the culvert, Pleurosigma baliicutn^ P. terry- 

 a?ni7)?,P. ostrigilis^ P. airiericanum^ P. decorum^ P.elongatum^ 

 P. {Colletonemd) cxhiihim^ P. brebissonii^ P. jfasciola, P. 

 paradoxuvi^ P. aiigtilatum^ P. affifie^ and many others, with 

 sigmoid Nitzschia^ large and small, in such annoying abundance 

 that it was impossible to sej^arate the Plciirosigvia so as to make 

 a satisfactory slide. 



In my description of the diatoms of New Haven harbor and 

 neighboring waters, published some years ago in this Journal, I 

 mentioned that Pleurosigma angiilatuni was universally dis- 

 tributed in these waters. In this statement I was misled by va- 

 rious experts to whom the slides were sent for determination ; I 

 now find that the species they called aiigulatian was P. ajffine^ 

 which is found nearly everywhere on the Connecticut shore, P. 

 angulatiiin being comparatively rare in deeper waters, and appear- 

 ing only occasionally in the shallow water of ditches and tide-pools. 

 The large P. balticutn var. maxime is found in nearly all the 

 shallow tide-pools near the open salt water ; with it frequently 

 appears P. cloiigatum^ and sometimes P. angidatiim ; the tide- 



