CALIGOIDEA. 1323 



extremity of the mandibles stand nearly at right angles with the pre- 

 ceding part, and to give the organ in this part better support, there 

 is, just above the insertion of the corneous extremity, a short lateral 

 bony process. 



In mouths of the more slender variety, the opening is terminal, 

 and the mandibles are straight, or nearly so. 



The mouth and its organs correspond normally to the upper and 

 under lips and the mandibles of other Crustacea. 



The maxillce are of two types. In species of Caligidse with the 

 obtuse or ovate trunk, as in Caligus, the maxilla? are a little distant 

 from the mouth either side, and have the form of a very large and 

 stout spine lying on its side, and pointed backward with one or two 

 points ; and there is usually a minute second joint on its under sur- 

 face, bearing two or three spinules (fig. la, and d, Plate 93). In 

 species with a slender pointed trunk, the maxilla is a small lamellar 

 organ, directly embracing the sides of the trunk towards its base. 

 Three joints may sometimes be distinguished, the first nearly of the 

 size of the whole organ, a second quite small, and the third a minute 

 terminal point. 



Legs. — The first pair of feet consists, in most species, of three oblong 

 slender joints, with sometimes a short basal. The second joint is 

 much more slender than the preceding, and not shorter; and its lower 

 apex is prolonged to a very slender point ; and where this prolonga- 

 tion begins, the third joint arises ; this resembles the apical process of 

 the preceding joint alongside of it, and both together form a kind of 

 bidigitate termination to the legs : each has generally a very minutely 

 pectinated edge. 



In Argulus, the legs of the first pair are very large tubular, and 

 have a broad rayed margin for attachment, the rays of which, when 

 highly magnified, are moniliform (Plate 92, fig. 2 e). In Nicothoe, the 

 leg approaches the form in Caligus ; but the first joint is stouter, and 

 the second or last is long and somewhat hooked. 



The second pair of legs is stout in all the species, and generally it 

 is well fitted for prehension, especially in males. In male Caligidse it 

 has often the form of a thick didactyle hand (fig. 3/, Plate 92); but 

 in some females it is not half as stout, and is monodactyle (3/'), the 

 moveable finger being longer, but not closing against a process on the 

 preceding joint, none existing for this purpose. The fingers are some- 

 times in a transverse position with reference to one another, but at 



