NEW FORMS OF MARINE DIATOMACE^. 513 



This form, like most of the preceding Amphorae, occurs both in Lamlash Bay 

 and in Loch Fine ; but it is not so frequent as most of the others. It is conspi- 

 cuous from its length. 



72. Amphora Icevissima, n. sp. PI. XII., fig. 72. Form elliptic, rather nar- 

 row, ends subtruncate. Aspect remarkably hyaline. Length 0-0025" to 0003"; 

 breadth 0-0009". The inner lines in each valve rise from the inner angles, bend 

 suddenly outwards for a short distance, then gently inward to the nodule, leaving 

 a very narrow inner compartment at each end. The middle of each valve is tra- 

 versed by a strong bar or elongated nodule. The valves are transversely striated, 

 but the striae are so fine, and the valves so hyaline, that the striation has not 

 yet been perfectly resolved. 



This delicate species is not very rare in the Loch Fine dredging noticed under 

 A. turgida as rich in Amphora?. But the detached valves are much more fre- 

 quent than the entire form. These detached valves have a resemblance in form 

 to the valve of A. elegans, figured in my last paper on the Glenshira Sand 

 (Trans. Mic. Soc, vol. v., pi. i., fig. 30). But A. elegans is a considerably larger 

 form, and not particularly hyaline ; while its striae are much less fine, and thus 

 easily seen. 



73. Ainphor a pellucida, n. sp. PI. XII., figs. 73 and 73 b. Form a broad oval. 

 Length from 0-002" to 0-003"; breadth from 00012" to 00018". Valves arcuate, 

 very convex on the dorsal, slightly concave on the ventral surface. There is 

 something very peculiar in the aspect of the terminal parts of the inner margins 

 of the valves, as these coincide with the terminal nodules, which, from the 

 delicacy and transparency of every other part of the inner margin of the valve, 

 appear to project like horns, as the nodules not only coincide with the ends of the 

 inner margin, but are narrow and much elongated. The inner lines follow the 

 margin for a little, then bend rapidly outwards, and then as rapidly inwards to 

 the central nodule on the ventral margin. The ventral margin, except at the 

 nodules, is so hyaline as to be seen only on close inspection, as are also the spaces 

 lying between it and the inner curve-lines. The space outside of these latter 

 curve-lines is striated, the striae rather coarse ; but the whole is so hyaline, that 

 the striae are only seen on very close inspection, when they come out plainly. 

 They are somewhat inclined, thicker and more easily seen at the outer margin, 

 very delicate and nearly invisible towards the inner one, and about 30 in 0-001". 

 There is a narrow, rectangular space between the two valves. Sometimes the 

 form of the frustule becomes nearly rectangular, but all its other characters 

 continue as before. 



The form of the valves, as well as of the entire frustule, in this species, is some- 

 what similar to that of A. ovalis. But, not to dwell on the marine habitat of A. 

 pellucida, its very hyaline aspect, and the singular delicacy of the striae, which are 

 entire, and, towards the nodule, become so fine as to be hardly visible, effectually 



VOL. XXI. PART IV. 6 Y 



