NEW FORMS OF MARINE DIATOMACE^]. 515 



but lying nearer to the inner margin. On these lines are faint nodules, while at 

 the middle of the inner margin there are distinct nodules. Length 0-0025" : 

 breadth 0-0011". The whole is marked by transverse stride, which also traverse 

 the openings between the valves, in which openings a median line is also visible. 

 Striae fine, subdistant, about 24 in 0-001". The divergent extremities are joined 

 by a convex curve line. 



This very peculiar species occurs, but very sparingly, in Lamlash Bay. It has 

 some analogy with A . marina, a form lately figured by Professor Smith, in the 

 Annals of Natural History (January 1857, vol. xix., pi. i., fig. 2.) But besides 

 the coarser striation and distinct nodules of A. dubia, Professor Smith describes A. 

 marina as so much resembling A. affinis, that it has been confounded with that 

 species on our coasts. Now A. dubia has no resemblance whatever to A. affinis, 

 nor indeed to any other known species ; so that I have some doubts as to its being 

 really an Amphora. The figures of A. marina given by Professor Smith are not 

 satisfactory, for they do not at all resemble A. affinis. 



77. Amphora truncata, n. sp. PI. XIII., fig. 77. Form of frustule slightly barrel- 

 shaped, broad, with truncate ends. Length about 0-0028" ; breadth about 0*0017". 

 Valves arcuate on dorsal, straight on ventral margin. Inner curve lines arise 

 from the terminal margin, and bend gently inwards to a small nodule, rather 

 nearer the inner than the outer margins. Inner margin of valve marked by a lon- 

 gitudinal line of short transverse striae. In the rectangular space between the two 

 valves, which is broad, are two similar longitudinal lines of short striae, near to, 

 and parallel to those just mentioned, and between the two last-named lines or 

 bars are traces of others. Valves transversely striated, but the striae are more 

 conspicuous on a band at the outer margin, than elsewhere. So that the frustule 

 appears, at least in a certain focus, marked with longitudinal striated bands, 

 formed of short striae. 



This species is not very rare, in either of the two gatherings so often named 

 in connection with Amphorae. It frequently happens, that the line joining the 

 ends of the valves appears to be interrupted in the middle. But by careful focus- 

 sing it may be seen. 



The appearance of longitudinal striated bands on the middle part of the frus- 

 tule seems to indicate a tendency in this species to the complex structure. In- 

 deed, among the complex species there is one, A. quadrata, which has consider- 

 able analogy with the present form . 



78. AmpJwra oblonga, n. sp. PI. XIII., figs. 78, and 78 b. Form linear elliptic, 

 rather broad, the ends obtusely acuminate. Length from 0-0034" to 0004' : 

 breadth from 0-001" to 0014". The inner curve lines are strong and much 

 curved, but they keep unusually near the outer margin of the valve, only in the 

 middle projecting rather more than half way across. The central nodules, which 

 are conspicuous, are situated outside of the carve lines, and nearer to the outer 



