320 The Entomostraca of Mid-Lothian. [Sess. — 
fifty or sixty creatures all swimming in an identical way, and — 
one or two others among them swimming in a slightly different — 
way, the latter catch the eye at once. So much so, that we 
have frequently taken up in the dipper some creature which 
was swimming in an unusual way, and found that it was 
merely a common species which had either lost its tail or was 
hindered in its movements by a swarm of parasites. 
Eurycercus lamellatus is a somewhat ungainly looking 
creature, but excites admiration by the wonderful saw with 
which the postabdomen is furnished. In a large specimen 
there may be as many as one hundred teeth in the saw, 
gradually increasing in size towards the large terminal 
claw. 
The various species of Alona are occasionally difficult to 
distinguish ; we have sometimes, for instance, found ourselves — 
unable to decide whether a certain specimen was afinis or 
quadrangularis: the typical A. afinis has a distinct tuft of — 
hairs just below the terminal claw, and the typical A. 
quadrangularis has none; but when we find a specimen 
with one or two small hairs, it becomes difficult to say to 
which species it should be referred. 
Alonelia nana is the smallest of all our species; it is, as 
Brady remarks, easily distinguished from other lynceids by 
having the shell striated in the reverse direction. 
Acroperus harpe is a very common species; numbers may 
often be seen floating on the surface of the water. It seems 
that they get caught by the surface tension and are unable to 
free themselves from it. We have often released one from 
this position and squirted it into the water, and seen it swim 
off apparently none the worse. 
Alonopsis elongata we found in only one locality—Marfield 
Loch. It is at once distinguished by its long narrow shell 
and dark brown colour; and also by the small lines of 
striation running obliquely between the larger lines on the 
shell. 
Peracantha truncata we only found on one occasion, in the 
High Pond, Penicuik: it has a row of strong curved teeth 
along the posterior margin of the shell, which gives it a very 
characteristic appearance. We were surprised at the scarcity 
of this species in Mid-Lothian, having found it very frequently 
