310 THE VOYAGE OF H.M.S. CHALLENGER. 



of the mouth," a feature on which Mr. James Yates Johnson founded his genus 

 Funchalia. 



Posterior to the mandibles lie the two flattened pear-shaped metastomata. 



The first pair of siagnopoda is three-branched, the two inner being flat and leaf- 

 like, having the inner margins fringed with short spine-like hairs, and the third or 

 outer articulating at right angles with the preceding. 



The second pair of siagnopoda is three-branched ; the two inner or basal are 

 biramose, foliaceous, and tipped with short spine-like hairs ; the third is short, flat, and 

 pointed; outside this a large mastigobranchial plate is produced anteriorly to a rounded 

 extremity, considerably in advance of the other parts of the appendage, and projects 

 posteriorly, and diagonally outwards, as a valve closing the exit passage from the branchial 

 chamber, the whole being fringed with finely ciliated hairs. 



The third pair of siagnopoda consists of a broad, concavo-convex inner plate that is 

 fringed with hairs, a slender three-jointed branch that represents the true limb of the 

 appendage, behind which, and closely associated with it, is a broad membranous plate that 

 at the distal extremity suddenly narrows to a point, and has at its base a broad but 

 short mastigobranchial plate. 



The first pair of gnathopoda is subpediform, having the three distal joints reflexed on 

 the inner surface and thickly studded with hairs ; the basisal joint carries a long ecphysis, 

 and the coxa supports a mastigobranchial plate bearing a rudimentary podobranchial 

 plume at the base. 



The second pair of gnathopoda is pediform, longer than the first, and extended in 

 advance of the frontal margin ; it is generally fringed with hairs and terminates in a 

 very straight dactylos capable of being bent to a right angle. The basis carries a long 

 ecphysis, and the coxa supports a mastigobranchial plate that bears a podobranchial plume.- 



All the pereiopoda are without an ecphysis ; the three anterior pairs, which are 

 chelate, support a mastigobranchial plate, carrying a podobranchial plume. The two 

 posterior jmirs are not chelate and are less robust, the fourth supports a mastigo- 

 branchial plate without a podobranchial plume, and the fifth pair has neither. 



The arrangement of the branchial appendages is represented in the following table : — 



Pleurobranchise, 

 Arthrobranchise, 

 Podobranohise, 

 Mastigobranchue, 



The ventral surface of the female varies somewhat in the different species, but it 

 appears generally to be provided with a hollow or deep depression, posterior to the pointed 

 thelycum, in which apparently at certain periods a membranous substance is developed 

 or deposited, the use of which is yet to be determined (vide PI. XLIX. figs. 2, 3). 



