1893.] 



MICROSCOPICAL JOURNAL. 



47 



pool and ditches fartlier from salt water and more nearly fresh 

 occasionally contain P. terryatnini^ sometimes mixed with P. 

 balticutn^ but frequently entirely pure. P. americaniini is found 

 chiefly in the \vaters of tidal creeks, and P. decorum and the 

 smaller form of P. balticjnn in the more saline and deeper 

 waters of coves and bays. The native habitat of Actinocyclus 

 barkleyi is on the bottom of the larger tidal creeks, or in ditches 

 and marshes of an estuary of a fresh- water river. 



The tide-pools in the marshes on the banks of Branford river 

 are very rich in P. halticmn ., and some of them contain P. 

 anoru/atiifn. Snrirella striatula and the largfer siemoid 

 Nitzschia are also abundant. The fossil deposit of diatoma- 

 ceous clay underlying these marshes I have had but little oppor- 

 tunity to examine, as no excavations have been made. It differs 

 from the others described, in that the upper layer just below the 

 peat contains abundance of Campylodisciis echciieis^ so that 

 slides can be made from it in which the Cainpylodiscus is 

 entirely pure. The stratum just below this is very rich in 

 species, somewhat resembling the Leete's island deposit. Dr. 

 D. B. Ward sends me the following determination of the forms 

 in a single slide from this stratum of the deposit which I sent 

 him, marked No. r, B : 



Coscinodiscus excentricus. 

 " oculus iridis. 



'' subtilis. 



" radiatus. 



Scoliopleura tumida (abundant). 

 Nitzschia acuminata. 

 " sigma. 

 " elongata. 



" plana (and several others). 

 Actiiioptychus undulata. 

 Tryblionella hantschiana. 



" punctata. 



Cyclotella striata. 

 Rhabdonema adriaticum. 

 Surirella febegerii. 

 " striatula. 

 " fastuosa var. 

 Coconeis scutellum. 

 Melosira sulcatum. 



Pleurosigma balticum. 

 " affine. 



" formosum. 



Navicula formosa. 



" marina. 



" formosa var. hiburnica. 



" erucicula. 



" elliptica. 



" peregrina. 



" oblonga. 



" lyra. 



'' interrupta. 



" digita radiata. 

 Campylodiscus echeneis. 

 Py.\illa baltica. 

 Tropidoneis seriata. 

 Raphoneis amphiceros. 

 Plagiogramma gregorii. 

 Amphiprora conspicua. 



Stauroneis gregorii. 



He adds : "There are several Nitzschias and A?)ip/wras 

 which I did not look up." 



The stratum next below this is of finer clay, containing mostly 

 lighter varieties, with many species of Pleurosigma. 



Dr. Ward determines two of the forms to which I called his 

 attention as : " Priceraiium {^dltyluini)bright'xvellii \^x. iiiae- 

 qualis Grun. = Dityliuvi inaequale Bail. 



'''•Navicula ( Van Heurckia) rJiomboides var. amphipleu- 

 roides Grun. Cleve & Grunow, Arctic Diatoms, PI. iii, f 59." 



I have so far examined only the three uppermost layers of the 



