Crangon and Galathea. 109 



fringed on its margins, likewise extending into the mouth, and a superior, which 

 is somewhat semi-ovoid in shape, fringed with articulated hairs, traversed by 

 vessels, and lying on the upper part of the branchial cavity, which it completely 

 covers. The basis is membranous for its upper two-thirds, broadly triangular ; 

 its distal margin ciliated, two-lobed ; its base calcified, narrow, and enveloped 

 in the respiratory plate. The ischium is likewise dilated, bifid, semicalcified, 

 arising above the basis in a notch in the superior lobe of the respiratory plate, 

 and bears on its external margin, near its base, a curved accessory appendage, 

 which is dilated at its base, pointed, and fringed with hairs at its apex. By 

 some this may be looked on as the meros ; but a comparison with the other 

 limbs is suiRcient to point out its true homologies. 



The third maxillie (seventh pair) (Plate X. 7) three-jointed, the coxEe 

 narrow, furnished with a simple respiratory plate {z), from which the accessory 

 appendage (jc) springs ; its basis is quadrilateral, membranous, attached for its 

 entire length to the border of the coxa ; the ischium elongated, flat, its inner 

 margin armed with rows (generally three) of fine chitinous teeth, internal to 

 which is a raised, chitinous ridge. 



The internal maxillipeds (eighth pair) (Plate X. 8) with six free joints, the 

 coxEe soldered as before; the basis is squared and short; the ischium toothed 

 on its inner edge, which bears a double ridge, and is fringed with iiairs. * The 

 accessory appendage {x) is made up of two joints, the basal longer than the en- 

 tire limb, somewhat cylindrical, dilated externally, its apical segment cylindri- 

 cal at the base, flattened, and ciliated at the apex. The meros is long, curved, 

 with a double frincre of stiff hairs along its inner margin. The three succeed- 

 ing joints are short and cylindrical ; the propodos and dactylos terminating in 

 bunches of stiflF hairs ; the dactylos is omitted in the figure. 



The external maxillipeds (ninth pair) (PI. X. 9, and PI. XV. 9) are seven- 

 jointed. The coxa short, somewhat triangular, its external inferior angle dilated 

 into a long process, which bears a set of branchiae. The secondary appendage is 

 four-jointed, arises from the outer superior angle of the coxa, and is articulated by 

 a lateral process to the basis. Its basal joint is short and imperfect; the second 

 long, curved, somewhat trigonal; the third short, slender; the terminal joint 

 curved, flattened, multiarticulate, and hairy. The basis and ischium are con- 

 nate, the line of junction marked by a suture, the inner edge dilated, hollowed, 



VOL. XXIV. Q 



