June 1, 1SG7.] 



HARDWICKE'S SCIENCE-GOSSIP. 



133 



MONMOUTH DEPOSIT. 



THE Editor of this journal Laving received from 

 the Rev. E. C. Bolles, President of the Portland 

 Institute, a quantity of a rich diatomaceous deposit 

 from Monmouth, Maine, U.S., for distribution under 

 the conditions named in the exchange list, I have 

 acceded to his request to furnish an account of the 

 forms which this deposit contains. 



It resembles the majority of the American fossil 

 fresh- vrater deposits, namely, those of New York; 

 Wellington, Counecticut ; New Hampshire ; Blue 

 Hills, Maine ; Cornwallis, Nova Scotia, &c, in being 

 very rich in the genus Pinnularia. It also resembles 

 the Bergmchl found iu Lapland, in containing many 

 species of Eunotia. 



This deposit is perhaps the most purely dia- 

 tomaceous of all that I have been fortunate enough 

 to obtain. No action takes place on the addition of 

 acids, showing the absence of any calcareous matter, 

 thus indicating that the water in which the diatoms 

 lived was free from lime. The diatoms are un- 

 usually perfect, and the strife upon the more delicate 

 species are as easily resolved as those upon recent 

 forms. 



. 





140. 



Fig. Ml. 



The following are some of those which I have 

 found in this material. Pinnularia gigas of Ehren- 

 burgh, and Pinnularia major of Kutzing, the latter 

 figured in Science-Gossip for 1S66, and repeated 

 here (fig. 140). These species, together with Pinnu- 

 laria nobilis and Pinnularia mesogongyla, might 

 with propriety be made one species, as their specific 

 differences are not sufficient to warrant their separa- 

 tion. Ehrenberg gave a figure of Pinnularia gigas 

 in the Mikrogeologie (plate 2, 3, fig. 1). 



Pinnularia dactylus of Ehrenberg resembles the 



above-named in its conspicuous costae, but differs 

 in the apices being slightly narrower, and the centre 

 not inflated. 



Beside these, may be found Pinnularia stauroeni- 

 formis of Smith (figs. Ill and 112), Pinnularia 

 divergens of Smith (fig. 143), and Pinnularia acro- 

 s pha;ria of Smith (fig. 1 I 



-■:. 



Fig. 142. 



Fig. 143. 



Fig. 144. 



The genus Navicula is represented by Navicula 

 Bacillum of Ehrenberg, Navicula dilatata of 

 Ehrenberg, and Navicula amphigomphus of Ehren- 

 berg. The two latter are scarcely sufficiently 

 distinct to warrant their separation. Navicula 

 microstoma and Navicula firma are probably only 

 varieties ; the appearance of longitudinal lines near 

 the margin is caused by the curved margin of the 

 valve, as I hope to explain by the aid of figures in 

 a future paper on the forms in this deposit, which 

 contains a very beautiful variety of this species. 



■v m 



Fig. 145. 



Fig. 148. 



Navicula Trochus of Ehrenberg was first observed 

 in a fossil deposit from Sweden, and has since been 

 detected in several of the American deposits, and by 

 G. Norman, Esq., of Hull, in a recent gathering from 

 Norway, and by myself iu the washings of some moss 

 gathered in Heigham, Norfolk. This, although a 

 small form (the largest specimen 1 have seen did 

 not exceed T400 of an inch in length), is readily 

 detected by its peculiar form. It has a strongly 

 inflated centre, with rostrate and obtuse apices. 





