ORDER CRUSTACEA HOMOBRANCHL^. 135 



The Opossum Shrimp belongs to a group of crusta- 

 ceous animals which have been called fissipeds, {split- 

 feet,) on account of each of their feet being divided nearly 

 throughout its whole length ; the inner limb being 

 constructed for progression and the seizing of their 

 prey, and the outer for swimming and giving that 

 motion to the water which is essential to the organs of 

 breathing, which are, as it were, wrapped round the base 

 of each limb, and fully exposed to the action of the ele- 

 ment. In the other Crustacea, which they most nearly 

 approach, such as shrimps, prawns, &e., there is a 

 single row of five feet on each side : but the genus we are 

 now describing possesses as many as four rows of feet, 

 each containing eight, so that in all, the number of feet 

 amounts to as many as thirty-two, — sixteen adapted for 

 swimming, and sixteen for seizing their prey. In con- 

 sequence of this organization, the Shrimps seek their 

 food in the sands at the bottom, while the present genus 

 frequent the surface. 



The most singular portion of their formation, and that 

 to which they are indebted for a name, is a kind of pouch 

 which the female possesses, fixed beneath the body, and 

 formed of two concave pieces of shell ; this pouch, which 

 is very capacious, considering the size of the animal, is i 

 destined to receive the eggs, which are deposited in it, 

 enveloped in a kind of jelly-like substance, most pro- 

 bably forming the food of the young when first hatched. 

 As fast as the young assume the lengthened form of the 

 perfect animals, they are found to arrange themselves in 

 this pouch closely and regularly side by side, with their 

 heads towards the breast of the mother. After this 

 manner they lie closely compacted together, and present 

 a perfectly symmetrical arrangement, easily observed 



