ON MYSIS. 25 



to the iiumeiliate service of auxiliary jaws) the whole 

 series of feet to the number of eight pair, arc thoroughly 

 developed, and further, present us with a very peculiar 

 construction, being all divided to the basil joint or coxipj 

 into an outer and an inner branch ; the former correspond- 

 ing with the flagrum in the Decapoda, having each a 

 branchia wrapped around their first joint, and ending in 

 a pluri-articulate plumose member, adapted to swimming; 

 the latter or inner division, constitute the true feet, and 

 except in the two anterior pair, end in a many-jointed 

 tarsus surmounted by a small hook, this part in the two 

 anterior ones, being reduced to two joints, of which the 

 extreme joint resembles a kind of hand more or less com- 

 plicated, particularly beautiful in the second pair, being 

 furnished with a marginal row of jointed spines, most 

 elegantly toothed on their opposite edges. 



Valvular pouch. Attached to the base of each of the 

 inner divisions of the two posterior pairs of feet in the 

 female, is a large concave scale, strongly pectinate in 

 front, of which the posterior is the outermost, largest, 

 and most concave, lapping considerably over the anterior 

 scale, so as to admit of a considerable extension of the size 

 of the pouch which they fonii, by meeting each other in 

 front, in order to accommodate its capacity to the growth 

 of the ova and young brood. 



In the male in place of the valvular pouch of the 

 female, we perceive attached to the inner part of the 

 last pair of feet only, a single small hollow scale on each 

 side, ciliate in front, and provided with a marginal row 

 of slender hooks at the apex : these are probably an 

 appendage of the male organs, which have a similar 

 situation in the Shrimps. 



The Abdomen or caudal extremity, consists of five 

 joints, furnished beneath with as many pair of fins or 

 natatory members, each fin composed of a single elongate 

 flattish scale, plumosely ciliate on its outer margin. We 



D 



