ANIMAL NATURE OF DIATOME^. 481 



Kiitzing does not acquaint us with his authority for 

 referring as a doubtful synonym of this species to the 

 Isthmia vesiculosa of Agardh, which, from that author's 

 description, would rather appear to be a Desmidiea. In 

 my monograph of the Desmidiese (1840), I had regarded 

 this species as the type of a genus, which at that time 

 was by Kiitzing denominated Isthmosira. 



I have not happened to meet with the J. adriatica. 

 recently published by Kiitzing, {Fhycologia Germanica^ 

 p. 115,) which, by the strong prominence of its angles, 

 is much more allied to the Isthmiee. 



It is to be observed, that this projection varies very 

 much in the preceding species, as stated by Ehrenberg, 

 and as I have observed in the specimens before men- 

 tioned. The other species, J. parallela, which hitherto 

 has only been found in a fossil state, seems to be very 

 distinct. 



63. Amphipentas. — Individua pentagona. 



Both species of this genus are of a doubtful nature. 

 Collecting here together all that is referable to the family 

 of Anguliferse, {Lithodesmium, Amphitetras, AmpMp-entas,) 

 I can only repeat what was before said of the second of 

 these genera. The first is uncertain in its nature, but, 

 at all events, can have no aflfinity with the second. The 

 last has some resemblance, at least in external ap- 

 pearance. 



The two families, Coscidoniscese and Anguhferse, con- 

 stitute the order Disciformes. I know not what character 

 can have led Kiitzing into this union, for the very name of 

 the second family contradicts that of the order. I believe 

 that the Coscinodiscese cannot be separated from the 

 Melosirese, and that the Anguliferse, excluding the 

 genus Lithodesmium, ought to be united to the Bid- 

 dulphiese. 



64. Tripodisctjs. — Individua sivgularia? libera?^ 



31 



