Desmldiece.^ infusorial animalcitle3. 241 



margins. The endochrome is divided into linear portions by a pale 

 transverse line between the angles. Traces of a mucous sheath may- 

 be detected. A transverse view shows that the endochrome has 

 thick rays corresponding in niunber with the angles ; these rays are 

 frequently cloven. 



Recent specimens are known from other genera by one or two 

 dark waved lines passing down the filament, caused by the twisting 

 of the angular filament. 



Desjiidium Swartzii. — Triangular, equal, with a single longitudinal, 

 waved, dark Hne, formed by the thii'd angle; end view tiiangular, 

 with the endochrome three-rayed. Filaments very fragile ; adhere but 

 slightly to paper ; twisted. The joints are, in the front view, some- 

 what quadi-angular, broader than long, and each angle has two 

 minute, slightly angular teeth. The joints are connected by a 

 thickened margin, which partly fills the notch formed between them 

 b}' the projection of their angles, whence the chain has a pinnatifid 

 appearance; transverse view, triangular; angles blunt, and sides 

 slightly concave. The segments contain numerous minute granules. 

 Length of joint I-2000th to l-1666th. Breadth of filament l-633rd. 



D. quadrangulatum, (Ralf.) — Quadrangular, varying in breadth 

 from the twisting of the filament, and having two longitudinal waved 

 Hues ; the end view quadi-angular, with the endochrome four-rayed. 

 Being quadrilateral, the filament presents two longitudinal lines 

 crossing each other obliquely. (P. 13, figs. 37 and 40; f. 40 a 

 transverse view.) Length of joint l-1244th. 



D. undulatum . — Joints with four crenatxu'es at each margin. 



The constriction of the joints is marked by slight marginal 

 notches, on each side of wliich are two broad crenatui'es; in this 

 respect D. undulatum differs from D. Stvartzii. 



D. didymum (Corda.) — Ehrenberg and Meneghni unite D. didymum 

 to D. hifidum (Ehr.) which the latter describes as a filamentous 

 plant. In D. hifidum, says Corda, there ai'e but two simple projec- 

 tions on each margin of a segment, but in D. didymum, the two 

 projections themselves present each, two secondary ones. 



D. hifidum (Ehr.) = Staurastrum hifidum (Ralfs.) 



D. orhiculare (Ehr.) = Staurastrum orhiculare (Ralfs.) 



D. hexaccrob (Ehi-.) = Staurastrum tricorne (Ralfs.) 



