440 MR JOHN RATTRAY ON A 



44. Surirella inaequisculpta, n. sp. (PI. XXIX. fig. 11). 



Valve linear, and slightly constricted in the middle. Extremities dissimilar, 

 both conical, but one much more acute at the apex than the other. Alse 

 parallel to the margin throughout. Canaliculi very variable in size and dis- 

 position throughout the valve ; towards the two extremities narrower, oblique, 

 and arcuate, the concavities being directed towards the apices, in the median 

 zone larger, transverse, mostly very faintly defined. Central area on valve much 

 reduced, linear, very indefinitely marked out. Clear areola at more obtuse 

 extremity small, subtriangular, with rounded sides and very blunt angles, that 

 at acute extremity still more minute, subrotund. No clear space intervenes 

 between this areola and the margin. 



Length, 0*2075 mm.; greatest transverse diameters, 0*0425 mm. and 0*0400 

 mm., the smaller towards the more acute extremity; transverse diameter of 

 median constriction, 0*0375 mm. ; distance between canaliculi in middle zone, 

 0*0062 to 0*0075 mm.; diameter of apical hyaline areola at the more obtuse 

 extremity, 0*0075 mm., that at the less obtuse end, 0*0050 mm. 

 Rare. 



Among the linear subpanduriform species of Surirella this frustule ap- 

 proaches Surirella arcta, A. S. (op. cit.,-p\. xxiii. fig. 23), in outline more closely 

 than any other, but it may be distinguished from it in several important 

 respects : — (1) the two apical cones are not similar ; (2) the terminal areolae 

 are not identical at both ends ; (3) the canaliculi are much more indistinct, and 

 at the extremities they are much finer and more arcuate. From Surirella gra- 

 cilis, Grun., it is distinguished (1) by its more marked median constriction ; (2) 

 by a more pronounced absence of uniformity in the size of the canaliculi at 

 various parts ; and (3) by the somewhat more arcuate appearance of the 

 extremities. The closely allied Surirella, angusta, Ktitz., may also be dis- 

 tinguished by the character of the extremities and canaliculi ; whilst Surirella 

 linearis, W. Sm., though also having close affinities, differs markedly in the 

 relatively much larger size of the valval ornamentation and the distinct 

 character of the terminal areolae. 



Tribe III. CRYPTORAPHIDIEiE. 



Earn. 8. Melosireve. 



45. Cydotella antiqua, W. Sm. 



Common, typical, and of various sizes. The following table gives the 

 diameter, number of cuneate cellules, and of marginal puncta in the valve in 

 several of the specimens observed : — 



