142 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
placed on the apex. Second (fig. 6) and third pairs of 
swimming feet nearly alike, the outer branches being 
composed of three joints, and the inner of one only, which 
has a slight constriction on its outer margin near the 
apex. In the fourth pair (fig. 7) the outer branch is also 
composed of three joints, but the inner branch is distinctly 
two-jointed, there being a small apical joint carrying one 
seta, and a moderately long basal joint. The fifth pair of 
feet (fig. 8) consists of one broad lamelliform shield, due to 
the complete coalescence of the basal joint of each pair. 
The end of the coalesced basal joints is rounded, with a 
slight concavity in the middle, on either side of which are 
two short sete. The length of the plate is equal to nearly 
two-thirds of the breadth at the widest part; outer 
branches very small, longer than broad, and bearing one 
marginal and two terminal sete. Abdomen composed of 
four segments, the first or genital segment being the 
largest, the second or third segments are nearly of equal_ 
length, the fourth segment is very small, being about half 
the length of the second or third. Caudal stylets (fig. 9) 
short and stout, the breadth being equal to about two- 
thirds of the length. There are three sete on the extremity 
of the inner angle, and one on the outer angle, with an 
intervening space. There is also one small seta on the 
outer margin near the base. The male is yet unknown. 
In the same gathering as the last; not common. 
This new member of the genus Leptopsyllus is easily 
distinguished from previously described species by the 
-elongate joint of the inner branch of the first pair of 
swimming feet, and by the structure of the fifth pair.* 
We have much pleasure in naming this species after 
Professor Herdman. 
* This species has recently been taken in the Clyde, off Millport, by 
T. Scott. 
