60 TERATOLOGY OF DIATOMS. 



ii. Same species, triangular form Triceratium striolatum, E. A group 

 of three specimens, of which two are the triangular forms, with regular 

 and moderately convex sides ; the other specimen has one such side, 

 but the other two curving into each other in a similar way to No. 2 

 above. The third process is wanting, but in its place are two spines, 

 such as appear on the sides of the regular Biddulphia lorm. Variation 

 in this species is so common that it would be easy to make a series 

 of photographs showing the gradual passage of the Biddulphia into 

 the triangular form. 



12. Eunotia diadema, E. Charleston, S.C. ; recent. The concave 

 side irregularly curved, making the width of the shell much less in 

 one place than elsewhere. The convex side is regularly eight-toothed. 



13. Eimolia monodon, E. Eoka Deposit, Sweden; fossil. A deep 

 irregular indentation on concave side near one end, making the shell 

 roughly comma-shaped. 



14. Eunotia arcus, E. Dolgelly Earth, Ireland (') ; fossil. A similar 

 (but less marked) irregularity. In a recent gathering at Cincinnati, 

 Ohio, these Eutwtias are found with so irregular reversed curves as to 

 resemble wriggling earth-worms in outline. A specific distinction has 

 been improperly based on this peculiarity. 



15. Licmophora ovata, E. Santa Monica, Cal. ; fossil. A large, shallow 

 indentation on one side, giving a gracefully varied outline. 



16. Rhaphoneis amphiccros, .Zs.- Savannah, Ga. ; recent. One side of 

 the shell a regular curve, the others very irregular. 



17. Cymaiopleura clhpiica, Bred. France; recent. The outline of 

 the shell on one side irregularly wavy. 



18. Grannnalophora marina, Kg. Algoa Bay, Africa ; recent. One 

 side wavy, unsymmetrical. 



II. Double or multiple centre in the scheme of marking. 



19. Mastogonia actinoptychus, Ehr.- Richmond, Va. ; fossil. Elliptical 

 form, with two distinct central spaces from which the costae radiate. 



20. Stictodiscus Cahfornicus, Grev. San Luis, Obispo, Cal. ; fossil. 

 A fine circular specimen with two centres, the radiating costse approxi- 

 mately regular on the outer limbs, but anastomosing in the space 

 between the two centres. 



21. Navicula Samoensis, Grun. ( = Nav. palpebralis, Gteg.l). Samoa 

 Islands, Pacific Ocean ; recent. In one half the shell, longitudinally, 



(') Wales. W.E.B. 



