NEW FORMS OF MARINE DIATOMACE^". 503 



diameter, but in the middle, in a line at right angles to this, extends to less than 

 half the diameter. Hence the canaliculi form a broad marginal band, except near 

 the ends of the median line, where it is narrow ; and the vacant space is ellip- 

 tical, suddenly contracted at the ends to narrow processes, which traverse the 

 band of canaliculi at its narrowest part to the very margin. At the roots of these 

 processes, the canaliculi suddenly recede from the median line. They are much 

 inclined at the extremities ; and the longest are from 00008'' to 0-015" in length. 

 The true median line is visible, and is very delicate ; but there are no other mark- 

 ings visible on the vacant middle space. 



The surface of the valve, both above and below, that is, near both ends of the 

 median line, is suddenly bent back, so as to form an angle with the rest of the 

 valve. On the surface thus bent, short lines appear, apparently between the ca- 

 naliculi, which lines terminate abruptly. The greater part of the valve, and espe- 

 cially that part on which are the canaliculi, is convex, which causes the canali- 

 culi to appear curved. 



This species is frequent in one of the Loch Fine dredgings, and occurs more 

 sparingly in two others. I have named it from the angular bending back of the 

 valve. 



54. Campylodiscus eximius, n. sp. PL XL, figs. 54 and 545. Form nearly or- 

 bicular, and sometimes nearly square, with the usual modifications. I have seen 

 one specimen spiral, like C. spiralis. Diameter of disc from 0*004" to 0"007" or even 

 0-008". Canaliculi strong, very numerous, about 150 in average specimens; con- 

 fined to a marginal band, the width of which is generally about 0*0007" or 00008'. 

 The middle space is pale and hyaline, and at first appears blank ; but on close 

 inspection is seen to be covered with pretty large, very transparent, round granules, 

 which are not arranged in any order, but indiscriminately scattered, like the points 

 in shagreen. The median line is marked by a raphe, the ends of which, as of the 

 middle space, do not, as in the preceding species, traverse the band of canaliculi. 

 There is, at each end, a small point of the middle space which indents the mar- 

 ginal band, that being a very little narrower there than it is elsewhere. 



This very fine and conspicuous form is very frequent in one Loch Fine dredg- 

 ing, and less so in two others. At first I thought it might be identical with C. 

 Hodgsonii, Sm., of which one example is figured as large as this form. But in 

 his description, Professor Smith describes the middle space as marked by strong 

 radiate lines, formed of large granules ; and although I have not seen any of C. 

 Hodgsonii of this large size, yet I find the small ones to agree exactly with this 

 description. Now in C. eximius, not only is the valve in the middle not marked 

 with strong radiate lines, but under a low power it appears at first sight blank ; 

 and the very transparent granules are in general quite irregularly disposed, and 

 only in some instances show faint traces of a linear arrangement close to the 

 marginal band. As far as I have been able to judge, I am satisfied that the small 



