166 Professor Smith's Conspectus of the Diatomacese. 



from Vancouver's Island, and T.striolatum = Biddulp>hia, Heiberg, 

 1 Dansk Diatomeer,' page 41, pi. 2, fig. 16. I have never seen 

 Biddulphia reticulata with spines like Triceratium armatum. 

 B. turgida bears a greater resemblance to the latter form. 



The genus Campylodiscus always appears to me to be the best 

 marked of any of the genera of Diatoinaceae ; all the species I have 

 seen (and I possess or have examined nearly all those figured and 

 described, besides many which are possibly new species), I find the 

 circular outline of the valve, its double flexure, and median spaces 

 of the opposite valves of the frustule at right angles to each other, 

 constant characteristics. I have noticed the twisted form of Suri- 

 rella striatula in the Salt Lake gathering, but it differs from the 

 flexures in Campylodiscus ; the latter has two bends at right angles 

 to each other, and also in opposite directions. In Surirella the 

 valve is not bent, but sometimes it has a twist in a spiral direction, 

 most conspicuous in Surirella spiralis, Kiitzing = Campylodiscus 

 spiralis of the Synopsis. 



Guano Diatoms, &c. 



Many of the forms found in guanos were at one time considered 

 to be extinct species, like the majority of those in the " fossil earths " 

 from Barbadoes,Virginia, Maryland, &c. The beautiful Aulacodiscus 

 formosus was thought to be peculiar to the guano known as Upper 

 Peruvian or Bolivian. A. margaritaceus was found rarely in the 

 Chincha guano, but more plentifully in that known as Californian 

 guano. A. scaber and A. Comberi occurred only in the Chincha 

 guano. I always had an impression that these forms, like many 

 others at one time supposed to be extinct, would one day be found 

 living in the harbour near the localities from which the guanos 

 are obtained, and perhaps other localities. A similar idea occurred 

 to my friend Captain J. A. Perry, of Liverpool, who took the first 

 opportunity of proving the truth of the surmise. In a letter just 

 received, he says, " When I went away my last voyage I made up 

 my mind to find out if there was any similarity between the forms 

 found in the Guanape, Chincha, and Peruvian guanos, the 

 Mexillones deposit, and the recent forms to be found in the various 

 harbours ; so I made gatherings in each of the ports we called 

 at, and to the astonishment of all of us here at Liverpool, I have 

 got in great abundance recent forms of those found sparingly 

 in the fossil material, such as Aulacodiscus formosus, A. margari- 

 taceus, A. crux, and A. Comberi, Omphalopelta versicolor, &c, &c, 

 which you will see much better than I can attempt to explain to 

 you." The recent forms are very fine, particularly 0. versicolor. 

 This to my knowledge had only been found in two localities, and 

 in both cases in a fossil state, viz. " Monterey earth " (not 

 "stone"), and described by Mr. Brightwell under the name of 



