TERATOLOGY OF DIATOMS. 59 



study of deformed diatom valves, and has published an excellent 

 pamphlet (') on this subject, a considerable portion of which I will proceed 

 to give : 



" I have," says the eminent American Diatomist, " provisionally 

 arranged them in three classes : i. Those having indented or deformed 

 outlines ; 2. Those having a double or multiple centre in the scheme 

 of marking ;' 3. Those having the marking unsymmetrically varied. 

 [Fig. 20.] 



I. Indented or Deformed Outlines. 



1. Navicula lyra E. Santa Monica, Cal. ; fossil. One side boldly 

 indented in a large, easy curve. 



2. Triceratium favus, E. Maranham Island, Pacific Ocean ; recent. 

 One angle is wanting, two sides being joined by a curve, making one 

 diameter, one-fourth less than the others. The process is present at the 

 deformed angles, but is unsymmetrically placed. 



3. Same species, from same gathering. A similar deformity carried further. 

 The form almost semi-lunar, but the curve is not regular. The third process 

 is wanting. 



4. Triceratium robust um, Grev. = T. Sculpt um Shadbolt ? Calvert Co., 

 Maryland ; fossil. One of the angles is replaced by two smaller ones, giving 

 an irregular trapezoidal form to the shell. 



5. Triceratium jormosum, Brtghtwell, var pentagonalis, Grun. Samoa 

 Islands, Pacific Ocean ; recent. One of the indentations between the points 

 of the star is nearly obliterated, and the two points connected by an irregular 

 curve. 



6. Same species and variety, from same gathering, similar deformity, but the 

 line connecting two points of the star is more nearly straight, showing a tendency 

 to revert to the triangular form of the type. 



7. Same species and variety, from same gathering. The deformity here 

 consists of a large umbonate protruberance in the centre of the shell, its 

 surface covered by the irregular marking. 



8. Same species, typical. San Luis Obispo, Cal.; fossil. A typical 

 triangular form, but with the central protruberance noted in No. 7. 



9. Biddulphia rhombus, W. Sm. Cuxhaven, North Sea ; recent. One side 

 deformed by a large, irregular indentation. 



10. Same species, same gathering. Similar deformity, but less pronounced. 



( ) Deformed Diatoms by Jacob D. Cox in Proceedings of the American Society of 

 Microscopists for 1890. 



