NATURAL SCIENCES OP PHILADELPHIA. 



13 



verge division, I am unable to say from actual observation ; but their ap- 

 pearance is certainly suggestive of that phenomenon. I ought to add, that 

 the secondary gibbosities on the ventral aspect of var. b., are rarely as well 

 marked as shown in the figure (13 b. pi. ii). 



Of Eunotia incisa, pi. ii., fig. 12a., represents an extreme variety. The ex- 

 traordinary attenuation of the valve well illustrates the synedroid bias, no- 

 ticeable in the Saco, and, to a lesser degree, in the Wolfboro muds. 



The inflexion peculiar to the terminal portion of the valve in these bacillar 

 varieties of E. incisa, often nearly reaches the dorsum. On the other hand, 

 an opposite variety of E. incisa occurs, which is nearly as broad as long.* 



Eunotia camelusl (fig. 126. pi. ii.) is probably allied to E. incisa. Some of 

 the frustules are long and narrow, with hardly any perceptible undulation. 

 = Eu. impressa, (Ehr.), occurs sparsely at Wolfboro and Bemis Lake. 



Eunotia bactriana, (Ehr.), (fig. 16, pi. ii.) is quite common. There appears 

 to be considerable range of variation in this species. 



Eunotia pentaglyphis, (Ehr.), as figured (fig. 4, pi. ii.) is also a changeable 

 form. It is widely distributed in the post-tertiary deposits, and has all the 

 characters of a metamorphic variety of Eu. robusta. 



Odontidium tabellaria, (Smith) = Dimereyramma tabellaria, (Ralfs.) I 

 have retained this name, as that by which this diatom is best known. The 

 two varieties figured in Smith's British Diatomaceae, and which may, for 

 convenience, be termed primary and secondary, seem to be peculiarly obnoxious 

 to the metamorphic force. Figs. 1 and 2, pi. ii., represent a series of elongated 

 varieties from the Saco river, (Synedroid). Of these, two are specially notice- 

 able, 2b, and 2d. The first of these has strong marginal puncta ; (Nitzschoid ?) 

 while the second exemplifies the same suggestive principle of symmetrical 

 variation seen in Himantidium undulatum, fig. 13, var. b. pi. ii. 



The punctate tendency, which is quite exceptional, manifesting itself only 

 on a few frustules, is to a lesser degree observable in Tabellaria, in the same 

 deposit. 



There remain to be considered, one or two forms in these deposits, which 

 are not clearly traceable to any known species. 



(1). Navicula (stauroneiform) n. sp. ? (pi. ii. fig. 9). F. V. not ascertained. 

 V. lanceolate, gradually attenuated towards the capitate or sub-capitate ex- 

 tremities. Striae sub-marginal, interrupted for a considerable space oppo- 

 site the central nodule. 



Hob. Wolfboro. Common. (Fig. 9, pi. ii.) 



This little form I have not named, as it may possibly prove a stauroneiform 

 variety of some known species. This stauroneiform habit is very obvious in 

 the Wolfboro varieties ; as is the synedroid, in the Saco. 



(2). Stauroneis Stodderii, n. sp. (Greenleaf), pi. ii. fig. 6.) F. V. 

 Linear, with slightly rounded ends ; connecting membrane slight and fragile. 

 V. elliptic lanceolate, with more or less produced and slender extremities. 

 Stauros linear, reaching the margin. Strive (longitudinal) parallel, sharp and 

 clear. Variable in number. Stria (transverse), radiant, distinct, about 55 in 

 001. Length variable. 



Hab. of St. phenkenteron and St. amphicephala. Bemis Lake, Wolfboro, Gor- 

 ham pond. 



This beautiful species was first made known to me by Mr. Stodder, who had 

 it from Mr. R. C. Greenleaf, of Boston, who names it St. Stodderii, in com- 

 pliment to the former observer. He has permitted me to describe it. 



*(Eunotia nodosa. Var. Himantidium pectinate? in the Bemis Lake, presents a remarkable 

 variety, analogous to the above in proportions. It is also nearly as broad as long, and slightly 

 constricted.) 



1865.] 



