260 MESSES. W. WEST AND a. S- WEST ON 



123. Staurastrum Brebissonii, Arch, in Pritch. Infus. ed. IV. p. 739. 



Var. HETERACANTHUM, nov. var. (PL XVI. fig. 26.) Minus, semicellulis spinis ad 

 angulum imumquemque paucioribus, cum spinis tiibus validioribus quam spinse 

 rcliquic ; a verticc visic lateribus subrectis. 



Long. 35 ^i; lat. sine spin. 35 /.i, cum spin. 50 /n; lat. isthm. llS /t. 



124. S. SETiGERUM, Cleve, in Ofvers. Sv. Vet.-Akad. Porh. 1863 (1864), n. 10, p. 490, t. iv. 

 fig. 4 ; Lund. Desm. Suec. t. iv. fig. 3 ; Eoy et Biss. in Ann. Scot. Nat. Hist. (1893) 

 p. 243, pi. 3. fig. 9. (S. Boyammi, Arcb. in Quart. Journ. Micr. Sc. xvii. (1877) 

 p. 103 : Cooke, Brit. Desm. p. 152.) 



Var. occiDENTALE, uov. var. (PI. XVI. fig. 7.) Var. semicellulis depressis, anguste 

 cllipticis, spinis ad angulos ut in forma typica, reliquis longioribus, paucioribus, et 

 irregulariter dispositis ; a vertice visis lateribus concavis, angulis rotundioribus. 



Long. s. spin. 31 n ; lat. s. acul. 38 ^, c. acul. 67 a* ; lat. isthm. 10 |U. 



This variety diff'ers mncli from the type in being broader than long, in the fewer 

 scattered spines, and in the concave sides of the vertical view. 



Var. PECTINATUM, nov. var. (PL XVI. fig. 28.) [=*S'. setigerum, WoUe, Desm. U.S. 

 p. 141, pi. 45. figs. 26, 27.] Var. minor, semicellulis spinis intra angulos validi- 

 oribus et longioribus (subcurvatis) ; sinu minus aperto. 



Long. s. spin. 34 n, cum spin. 44 ^ ; lat. s. spin. 31 ^, cum spin. 46 n ; lat. isthm. 6*5 n. 



Sab. Harvey Lake, Lycoming Co., Pa. 



125. S. MiNNESOTENSE, Wollc, Prcshw. Alg. of U.S. p. 43, 1^1. 57. figs. 7, 8. (PL XVII. 

 fig. 15.) 



Long. s. spin. 84-86 /u, cum spin. 117-128 ju; lat. s. spin. 71-78 fx, cum spin. 105-125 /t; 

 lat. isthm. 23-28 /x. 



The U\o spines at the angles are always stronger than the rest, and the latter are 

 generally somewhat irregular both in length and disposition. The only regular specimen 

 seen had nine pairs of spines to each semicell (fig. 15, h). In vertical view the sides are 

 slightly convex and refuse towards the middle ; the angles are not anything like so acute 

 as figured by Wolle. 



126. S. MAAMENSE, Arch. in Quart. Journ. Micr. Sc. ix. (1869) p. 200. [S.pseudocrenatumy 

 Lund. Desm. Suec. p. 65, t. 4. fig. 4.) 



The figure given by Wolle (iUg. U.S. pi. 57. fig. 10) of the front view of this species 

 is erroneous ; the drawing must have been made from a much tilted specimen, for the 

 warts would not otherwise show at the apices. All the American specimens we have 

 seen are similar to the European ones. 



127. S. suBSCABRUM, Nordst. Alg. Aq. dulc. et Cliar. insul. Sandvic. p. 16, t. 2. fig. 2. 

 Long. 27 /x; lat. 26 ^x ; lat. isthm. 7'5 /u. (PL XYllL fig. 12.) 



128. S. TRiHEDRALE, Wollc, Desm. U.S. p. 123, pi. 40. tigs. 12, 13. (PL XVI. fig. 29.) 

 We have found some examples which must belong to this species, the form of the ceU& 



