1900J MICROSCOPICAL JOURNAL. 317 



different rows seem as a rule to alternate more than in the 

 preceding species. It is the exceeding tenuity of the scales 

 which makes me refer the insect to the present species 

 (see Luhbock, p. 253). The scale would probably be a 

 good test object if difficulty of exhibiting the markings 

 were the only qualification. Seira buskii may give some 

 idea of these scales. They are of leaf-like shape, and have 

 a very small number of exceptionally large "exclamation 

 marks" ; altogether they look as if they might be a pri- 

 mordial or ancestral type of Podura scale. They might 

 be studied with advantage as throwing light on the struc- 

 ture of the scales of other Collembola, the marks, though 

 few in number, being so vastly larger than those of any 

 other species. I found the insect on ivy on a wall by the 

 railway at Shepreth, Cambs, in June 1886. Tomocerus 

 plumbeus or Macrotoma plumbea is a small, almost black 

 insect, of which I found a solitary specimen under a stone 

 in the woods at Colwyn Bay. This was almost the first 

 stone I examined, and although I looked under many 

 others I could not find any. This isan exceedingly pretty 

 scale, quite different from those of the other Collembola, 

 and approaching more nearly to those of the Thysanura, 

 Machilis and Lepisma. It has no "note of exclamation," 

 but instead has regular longitudinal striae, and between 

 them faint transverse striae as in Machilis, and also sev- 

 eral radiating corrugations starting from the pedicle cor- 

 responding to those of Lepisma. It thus combines two 

 different types of structure. Its dark color also helps to 

 render it a beautiful object. Machilis maritima is an in- 

 sect about half an inch long, brown with pretty mottlings 

 and white rings on the three long bristles, from which it 

 receives the name of "bristle-tail." It was simply swarm- 

 ing on rocks just above high-water mark outside the 

 mouth of the Dart, in South Devon, on the Kingswear 

 side, but was very difficult to catch and bottle. I got three 

 after trying for a long time. I have also seen it in abun- 



