\4^ KITTON, ON DIATOM ACE^. 



cured from Dredgings." In the following observations I 

 have assumed the amplification in the first paper to be the 

 same as that in the second, viz., 600 diameters. 



The following forms, described in the Rev. E. O'Meara's 

 papers (Vol. VII.), may, I think, be referred to previously- 

 described species. 



Navicula pellucida, O'M., fig. 2, is a state of N. Pandura 

 of De Brebisson. 



Navicula IVrightii, O'M., fig. 4. is certainly only N. clavata 

 of W. Gregory ; the striae next the median line being obli- 

 terated by abrasion. 



Navicula amphoroides, O'M., fig. 3, seems to be an 

 Amphora resembling A. salina of the Synopsis (= A. proteus 

 of AV. Gregory). Query, is not the nodule a small grain of 

 quartz ? 



Pinnularia constricta, O'M., fig. 8, jiossibly a form of 

 Navicula truncata, a very variable species both in size and 

 costge. 



Pinnularia divaricata, O'M., fig. 7, if correctly figured and 

 described, can be neither a Pinnularia nor Navicula, as none 

 of these genera have forked striae or costse. 



Surirella pulchella and gracilis * O'M., figs. 10 and 11, are 

 only forms of S. lata of the Synopsis, and this is merely a 

 variety of that most variable form S. fastuosa. In a good 

 gathering of this species, S. pulchella, S. gracilis, S. lata, 

 may all be detected, and probably a dozen other species if 

 slight differences in size, outline, or striation, constitute new 

 species. Dr. Greville, in* Trans, of Mic. Soc.,' 1862, p. 19, 

 makes the only difference between S. lata and S. fastuosa 

 to consist in the form of the median space ; but an examina- 

 tion of numerous sjoecimens proves that his only character is 

 of no value, for in specimens from the same locality all forms 

 of the median space appear. Dr. Gregory proposed uniting 

 his Campylodiscus simulans with S. fastuosa, but the former 

 is a true Campylodiscus having the poles of the opposite 

 valves at right angles to each other (a feature not peculiar to 

 C simulans or C. bicruciatus, in the Campylodisci the opposite 

 valves of the frustule are always in that position). C. bicru- 

 ciatus is only a frustule of C. simulans, and the latter is only 

 a large variety of C. parvulus. 



Coscinodiscus fasciculatus, O'M., fig. 1, Vol VII, is an 



* Herr Grunow describes and fijifures a/S*. gracilis. The following are his 

 specific characters : — " S. gracilis in (= Tryilionella gracilis, W. Smith ? ?) 

 Mittelgross, Schalen breit linear mit abgerundeten oder conischen Enden, 

 E-ippen 12 — 14 im O'OOl Im siisswasser." ' Verhand. der k.k. zoo.-bot. 

 Gesellschaft in Wien,' Band 12, s. 450, u. , Taf. vii, fig. 11. 



