SOME KOETH AMEKICAN DESMIDIE.E. 247 



This at first sight seems near to forms of C. pseudopyramidatmi, Lund., l)ut is miicli 

 smaller, more angular, less deeply constricted, and lias a different membrane. 



68. CosMARiUM suBDEPKESsrM, nov. sp. (PI. XV. fig. 15.) C. parvum IJ-plo latius 

 quam longius, profundissime constrictum, sinu angusto-liueari extremo ampliato; 

 semicelluhc multo depressge latissime reniformes; a vertice visa? oblonga^, laleril)us 

 rcetis et polls rotundatis; a latere visa^ circulares ; meml)rana minulissinia 

 punctato-granulata, pjrenoidibus binis. 



Long. 15-16 IX ; lat. 21-22 fx\ lat. isthm. 3-7 /* ; crass. 7'5 /i. 



This differs from C. depressum, Lund. (Desm. Suec. p. 38; Emstrum depressim, 

 Naeg. Gatt. einzell. Alg. p. 114, t. 7 c. fig. 2), in being much smaller and more 

 depressed, in having a narrower and deeper sinus, in its narrowly oblong vertical view, 

 in its binate pyrenoids, as well as in its very minutely granular meml)rane, wbich gives 

 the outline a very faintly rough appearance. 



69. C. SiNOSTEGOS, Schaarschm. in Magyar Tudom. Akad. Kozlcm. xviii. (1882) p. 266, 

 fig. 12. 



Var. OBTUsius, Gutw. in Nuova Notarisia (5 x4.pr. 1892) p. 21 ; et in Sj)rawozd. Akad. 



Krak. xviii. ii. (1893) p. 129, t. 2. fig. 13. 

 Long. 9"6 /tt ; lat. 105 ^ ; lat. isthm. 3'6 n ; crass. 5-5 /u. 



70. C. Clepsydra, Nordst. in Vidensk. Meddel. 1869 (1870) p. 212, t. 2. fig. 29. 

 Long. 20-22-5 ^ ; lat. 20-22 5 ^u ; lat. isthm. 5 /a ; crass. 17*5-70 ^. 



A form of this was observed with the sinus a little more open and with a Larger central 

 inflation ; the angles were also thickened and the membrane minutely punctulate. This 

 species and C. titJiophorum, Nordst. (Alg. et Char. i. p. 6, t. 16. fig. 6), seem to be closely 

 allied, and the American form might easily be placed as a variety of the latter species. 

 C. tithopJiorum forma intermedia, B. Eichl. & Gutw. (Nonn. Alg. Nov. 1894, p. 10, t. 5. 

 fig. 31), seems to be nearer C. Clepsydni, but with the angles rounded off. C. bicardia, 

 Heinsch, as figured by Borge, in Bihang Sv. Vet.-Akad. Handl, xix. (1894) Afd. ill. 

 n. 5, p. 31, t. 3. fig. 33, may possibly be a form of C, tithophorum, Nordst. 



71. C. ExmurM, Arch, in Micr. Journ. (1864) p. 178, t. 6. figs. 32, 33; Cooke, Brit. 

 Desm. p. 92, t. 43. fig. 4. 



Var. PRESSUM, West, New Brit. Freshw. Alg., in Journ. Roy. Micr Soc. (1891) p. 6, 



pi. 1. tig. 1. 

 Long. 16 p. ; lat. 67 /^ ; lat. isthm. 3-8 ^ ; crass. 4-8 ^x. 



T2. C. MINIMUM, West & G. S. West, in Trans. Linn. Soc. ser. II., Bot. v. (1895) p. 58, 

 pL 8. fig. 10. 

 Var. SUBROTUNDATUM, Wcst (/. c. fig. 11). 

 Long. 7-77 ju; lat. 6-7 a*; hat. isthm. 35 jtt; crass. 4 n. 



73. C. SUEIMPRESSULUM, Borge, in Bihang Sv. Vet.-Akad. Handl. xix. (1891) Afd. in 

 n. 5, p. 27, t. 2. fig. 27. 

 Long. 36-a8 fx\ lat. 25-5-27 ^; lat. isthm. 6-5-7-5 ^c; crass. 155 ^i. (PI. XV. tig. 18.) 



2m 2 



