ANIMAL NATURE OF DIATOME^E. 435 



Monnema Lenormandi, Ktz. in litt, (Schizonema.) 



Under the name of Schizonema Dillwynii, Lenormand 

 favoured me with a Monnema from Calvados, differing 

 greatly from the preceding. I wrote to Klitzing, who 

 replied that he had already created a species with the 

 name S. Lenormandi, sending me in confirmation a frag- 

 ment of his specimen. The Naviculae are 0' 02 5 5 millim. 

 in length, and attain a breadth of 0'04 in the primary 

 surfaces, when they are near the state of duplication. 



Monnema sordidum, Kiitz., (Schizonema.) 



Kiitzing establishes the length of the Naviculae ^ 

 ^th of the Paris line, or 0-02700-0225 millim., and 

 moreover refers to this species specimens from the lagunes 

 of Venice, corresponding in all other characters, the 

 Naviculae being 0'0245 millim. in length, and 0*0064 in 

 breadth, both on the primary surfaces, which are lineari- 

 rotundate, and on the elliptico-linear, obtuse secondary. 

 In a specimen with which I was favoured by Kiitzing, I 

 was not able to see the Naviculae clearly, but they seemed 

 to me somewhat smaller, not, however, so much so as in 

 this author's figure (5 millim. ^ s = 



Monnema Grevittei, Harv. 



This is one of the most instructive species, for the 

 Naviculae are frequently placed transversely, in such a 

 way as to demonstrate the total absence of partial tubes. 

 It is interesting also from the large size of the Naviculae, 

 which exhibit the process of duplication very clearly. In 

 these, too, Kiitzing saw the central aperture. In the 

 specimen with which I was favoured by Berkeley, under 

 the name of S. Gremllei (Alg. Danm.) and S. quadripunc- 

 tatum, Ag, I find the greatest dimension of the Naviculae to 

 be 0-034 millim. in length, and 0-016 in breadth, as well 

 on the primary surfaces, which are a sort of parallelogram 

 with the angles slightly rounded, as on the secondary, 

 that are broadly elliptico-obtuse. This differs little from 



