94' REVIEW. 



prora are certainly not so strongly marked in this species as 

 in others, but in the specimens I have noticed the connecting 

 membrane is slightly diagonal, the lobes of the valve do not 

 lie in the same plane, nor is the central nodule of the upper 

 valve exactly superimposed on that of the under one. Com- 

 paring the figure of Navicula siinulans, both on the side and 

 front views, with Smith's figure of Amphiiwora constricta, 

 I am disposed to doubt the identity, and to suppose that 

 Donkin's form^ is a new species. 



Pinnularia Pandura, Breb., has been correctly identified 

 with Navicula Crahro, Ehr., and N. nitida, Greg., as well as 

 iV. didijma, var. costata, Greg., reduced to the same species 

 of which, at best, they are but varieties. The description of 

 the species is exactly as it appears under a low power ; striae 

 interrupted by a straight longitudinal groove into a broad 

 outer and a narrow inner section, the latter consisting of a 

 longitudinal row of conspicuous hemispherical dots ; with a 

 higher power the striae are traceable down through the groove 

 and emerge again, the extremities appearing as an elevated 

 ridge along the median line. 



Dr. Donkin has greatly contributed to a more satisfactory 

 definition of the constricted forms of Navicula. Here there 

 has been great confusion, and though something more remains 

 to be done, there will henceforth be no difficulty in recog- 

 nising N. Apis, N. Bonibus, N. interrupta, not to mention 

 others. 



Eugene O'Meara. 



