Mr. C. Mcresclikowsky on Califominn Diatoms. 297 



60. Gyrosigma fasciola (Elir.), CI. San Pedro, common. [M.] 



fil. Gyrosigma Febigerii (Gruii.), CI. Laguna near San Pedro 

 in iitaily nnuiiu' water, rather common. [C, j\1.] 



62. Gyrosigma prolongatum, W. Sm. San Pedro, very 



common. [M.J 

 1 do not see any difference between G. prolonjatani ani 

 var. closteroides, Grun., the prolongations of the valve baing 

 turned on opposite sides or on the same side, according to 

 the jiosition of the frnstule. 



63. Gyrosigma Spencerii, var. exilis, Grun. Laguna near 



San IVdro, very common. [M.] 



64. Gyrosigma tenuissim urn, W. Sm. [C] 



6."). Gyrosigma Wansbeckii (Donk.), CI. Laguna near San 

 Pedro, rare. [M.] 

 Looks like G. haliicum, but the striai are much finer. 



In all the species of Gijrobigma above mentioned which 

 1 have observed myself, as well as in many others from 

 the Mediterranean and the Black Sea, 1 have invariably 

 found the endochrome to be com[)Osed of two plates, while in 

 all species of Pleurosigma (with the only exception of P. rigi- 

 clum, where it is granular) the endochrome consists of four 

 narrow, usually tortuous bands. This proves that Oyrosigim 

 and Fleurosigtna must be regarded as two natural and 

 distinct groups, which should not be united in one genus, as 

 has been done by certain diatomists. 



66. Mastogloia ^Orthoneis) Wrightii, O'Meara* (nee Clave). 

 (PI. IV. tigs. 22, 2;J.) Northern California, not rare. [M.] 

 Valve elliptic, with apices broadly rounded. 



Lenfjth: (H)lo (H)18 aOj^ 0020 0021 0-028 

 Breadth: OOll 00r2") (F014 0014 0^014 0020' 



Median line straight, enclosed between two parallel rows 

 of puncta not differing from the rest ; axial area linear, 

 distinct. Puncta of the valve forming transverse and decus- 

 sating rows, the tormer radiate, about 8-9 in 0"01 mm.f; two 

 of the median decussating ro.vs more distant, forming a 

 double lyie-like ligurc with both halves uniting at the centre 

 with the axial area; marginal rim narrow, with quadrangular 

 loculi, 8-9 in 0-01 mm. 



* ' Diatomeentafeln /usaiunun^i-estt'llt fur eiiiige Freunde,' pi. l.v.vvii. 

 tig. 0. 



t The cngmver did not succet-d in representnig' the great regularity in 

 the di-sposition of th(! puncta, the transverse rows which the latter form 

 being tlierefore in\ i.sible iu ti;jrures 22 aud 2-'J of the Plate. 



