PARASITES. 247 



and their homogeneous colouring. All these embarrassments are aggra- 

 vated by the living state^ — that alone from which I am wilhng to derive 

 information. 



There are few subjects to which this animal may be compared : it 

 would most resemble a diminutive instrument of sport, the battledore, 

 provided the single hand were divided into two tubular appendages, a 

 little apart. 



Thus, it consists of a thin convex shield or body, from the anterior 

 edge of which originate two anteunce, and from the posterior margin issue 

 two cylindrical tubes. Two black eyes, apparently merging in one, are on 

 the upper sui'face, near the anterior edge, and under it, the short tubular 

 proboscis. Eight limbs also issue from the under surface of the shield, 

 by which, or by means of part of them, the animal affixes itself firmly 

 and pertinaciously to its prey. 



It is extremely difficult to discover the number, the form, the posi- 

 tion of these organs, but they are what most naturalists agree to be the 

 complement of this species. The total extent of fine specimens may be 

 about seven lines, but there is a great disparity of size among them. 



Plate LXVI. 



Fig. 1. Caligns curtus, enlarged. 



2. Specimens nearly of natural size. 



3. Upper surface of a specimen, enlarged ; a, position of the antennae ; 



5, cylindrical tubes. 



It may be from the homogeneous colour obscuring distinct vision that 

 descriptions by difterent authors are discordant. Regarding one of which 

 MUUer treats, he says, Ocidi ei antenncB hitjus spccicbus difficulter deteguntiir ; 

 and he seems to assign the position of the former to the edge of the an- 

 terior portion. — Entomostraca, p. 128. Baster speaks of black eyes ; where- 

 on MUUer remarks, — E.v ocidorum caligine genus nomen sortitum est. — 

 P. 129. 



This parasite affixes itself by means of the limbs on the under sur- 

 face, to spots from which it cannot be dislodged without considerable 

 force ; therefore it must be a terrible persecutor. 



