28 BRITISH DESMIDIACE2E. 



C. pseudoconnatum is a smaller species than C. connatum, 

 with a slighter constriction and more rounded semicells. The 

 chloroplasts are also of a very different character from those 

 of C. connatum. It is a rare Desmid, and is principally con- 

 fined to small pools in the western areas of old rocks. 



Wille has described (' Sydamerik. AlgnV 1884, p. 18) a 

 ' forma major' from Brazil (length 76/z; breadth 50^u), and 

 Liitkemiiller has given measurements of Austrian forms of 

 about the same size (length 66-73 ju ; breadth 49-52 ju; 

 breadth of isthmus 42-44 ^). Turner has mentioned a small 

 form from India with a length of only 41 JJL and a breadth of 

 26-5^. 



Var. ellipsoideum West & G. S. West, (PL LXVII, 



fig. 22.) 



? Calocylindrus connatus var. minor Wolle, Desm. U.S. 1884, t. 12, . 55. 

 Cosmarium pseudoconnatum var. ellipsoideum West & G. S. West, Freshw. 



Alg. Ceylon, 1902, p. 168, t. 20, f. 43-45 ; Gutw. Alg. Ins. Java, 1902, 



p. 588 [under Pleurotseniopsis]. 



Cells slightly larger than usual, constriction some- 

 what deeper, apices of semicells often slightly flattened; 

 vertical view broadly elliptic. 



Length 56-63*5 /i; breadth 38*5-45 p.; breadth of 

 isthmus 32'5-38'5 ^ ; thickness 36 /i. 



Geogr. Distribution- -Burma. Ceylon. Singapore. 

 Java. 



This variety is as yet only known to occur in the Indo- 

 Malayan region, where it is met with much more frequently 

 than the typical form. The combination of a deeper con- 

 striction with a broadly elliptic vertical view is very 

 characteristic. 



It agrees fairly well with the figure of " Calocylindrus 

 connatus var. minor Wolle," which is most probably a form 

 of Cosmarium pseudoconnatum, but Wolle's published descrip- 

 tion and figure are insufficient to settle this point. We have 

 previously pointed out how very confused Wolle seems to 

 have been in his ideas of C. connatum and C. pseudoconnatum. 



We introduce this variety here because we have observed 

 some forms from Harris, Outer Hebrides, which appear to be 

 intermediate between it and the type. In front view they 

 possess a deeper constriction which gives them an outline 

 almost exactly corresponding to that of var. ellipsoideum, but 

 the vertical view is circular. Length 57-60 JJL ; breadth 

 39-42 u breadth of isthmus 33-36 . 



