28 LIVERPOOL BIOLOGICAL SOCIETY. 
piece or telson (i.e. the modified terminal segment of the 
pleon or abdomen) abnormal. 
The normal telson tapers gradually with almost straight 
sides to a narrow apex, which terminates in two strong 
and rather long spines, having two very small spines 
between them (fig. 1). In one of the males the abnormality 
consists only in having three instead of two small spines 
between them, but in the other three abnormal males and 
in the two females the spines at the apex are much more 
numerous, and are irregular in size and direction, and in 
one of the females the telson itself is markedly unsym- 
metrical, as shown by the drawing (fig. 2). 
Mr. Archer informs me that there is much sewage in 
the Alt, which may perhaps be the cause of the abnormality 
in question. Had only one of the abnormal specimens 
been taken without any of the normal form, it is easily 
conceivable that a new species might have been founded 
on it; the moral of which is that when one has a chance 
of securing a number of specimens one should always do so. 
NotE.—Since the above was written I have taken Mysis 
lamorne (Couch), at Colwyn Bay, in three fathoms, on the 
94th May, 1887. It was taken with other Crustacea in a 
dredge lined with canvas, and having the lips protected by 
round sticks fastened on them so as to prevent them from 
digging into the sand. 
