208 



Anaiihts birostratus, Grun. Very rare. 

 Atilacodiscits Solittiamcs, Norman, 



BiDDULPlilA Brittoniana, Kain and Schultze, n. sp. 



Valve oblong elliptical, terminating in apparently hollow, large 

 processes, which originate a little to the side of the extremities 

 and incline in opposite directions. From the base of each of 

 these processes arise one, and sometimes two, semi-circular, awl- 

 shaped spines. Along the margins and in the center the valve 

 is partly covered with a fine, hair-like growth, intercepted by two 

 longitudinal striated bands. (Plate XCIL, Figs. I, la, lb, ic). 



The structure of this very curious species seems, at first, 

 quite puzzling. The frustules appear to be formed of two valves 

 united with their convex sides together and the concave sides 

 outward — exactly contrary to received ideas as to the structure 

 of a diatom frustule. After a careful study of broken shells, it 

 will be seen that these apparent frustules are in reality valves oi 

 different frustules ; that the hoops, being easily destroyed, have 

 disappeared in the process of cleansing, but the setae being more 

 strongly sihceous, have withstood the treatment and held together 

 the valves of different frustules. 



In a specimen of Stauroneis acuta^ kindly furnished by Proi. 

 H. L, Smith, a similar phenomenon occurs. The hoops have dis- 

 appeared during treatment, and valves of different frustules have 

 united to form false frustules, in which the shells have their con- 

 vex sides together, and their concave sides outward. 



While the alternation of the sub-lateral processes indicates an 

 alliance with Ehrenberg's genus, Ceratatihis^ we prefer to adopt 

 the view of Professor Smith, who unites this genus with Biddulphia^ 



Figures I, la and ib are reduced from drawings kindly fur- 



nished by Rev. Francis WoUe. 

 Biddiclphia longispina, Grun. 

 Biddnlpliia WeissJIogii, Grun. 



BiDDULPHiA ? ? Kain and Schultze, n. sp. 



Valve broadly elliptical ; punctae irregular ; surface broken 

 by numerous free bands ramifying from the center ; two slight 

 elevations at each extremity. (Plate XCIIL, Fig, 4). 



While this curious form lacks the processes which belong ^o 

 the genus Biddnlphia^ it seems more closely allied to this than to 



