MANUAL OF NATURAL HISTORY. 293 



SI. Family. — Pencean-Shrimps (Penaeidae). Ab- 

 domen extremely elongated ; legs often with 

 a palpiform appendage at their base ; beak 

 short or wanting ; antennae very long ; legs 

 long and slender for swimming, last pair 

 rudimentary or wanting. 



32. Family. — Horned-Shrimps (Cerataspidae). Ca- 

 rapace large, sub-ovoid, tumid at the sides, 

 surface tubercled, prolonged inferiorly so as 

 to conceal the legs and antennae, leaving a 

 longitudinal fissure, armed with five horns, 

 one forming the beak, two on the sides in 

 front, and two behind these ; legs long and 

 slender with a lateral appendage ; abdomen 

 narrow. 



II. ORDER — Stomapods (Stomapoda). 



Gills external, on the abdomen ; head horny, se- 

 parated from the thorax ; mouth with three pairs of 

 jaws ; legs seven pairs, prehensile or for swimming. 



1. Family. — Opossum-Shrimps (Mysidae). Cara- 



pace slightly beaked in front ; mandibles with 

 a palpiform appendage on upper and lower 

 lip, and two lamellar jaws ; foot-jaws, each 

 with two well-developed branches at their 

 base ; abdomen moderate. 



2. Family. — Spectre-Crabs (Phyllosomatidae). Ani- 



mal transparent ; carapace large, lamellar, 

 horizontal ; thorax lamellar ; eyes large and 

 prominent ; mouth with a large upper jaw, 

 a pair of hooked mandibles, a membranous 



