392 STALK-EYED CRUSTACEA 



b. Carapace rounded. Frontal region has two 

 margins ; upper straight, lower projecting into a small 

 triangular tooth. — {Pisosonia.) 



II, First joint of the antennal peduncle more or less 

 produced, and joined to the margin of the carapace ; the 

 second joint placed at a distance from the orbit. 



c. Carapace suborbicular or subovate. 



c^. First pair of legs flattened ; fifth joint short, and 

 usually has a single projecting lobe near the proximal end 

 of internal margin. — {Porcellana}} 



d}-. First pair of legs large ; fifth joint longer than 

 broad, with entire margins ; front margin not dilated, 

 posterior margin arcuated. — {Megalobranchmm.) 



I. Petrolisthes. 



PetrolistJies Stimpson, Miers, Haswell, 



Henderson. 



Carapace subovate, depressed, the length usually 

 slightly greater than the breadth. Frontal region 

 triangular, usually depressed, with the margin more or 

 less undulating. Eyes rather large. First joint of 

 antennal peduncle remarkably sliort. First pair of legs 

 broad and flattened ; the fifth joint of moderate length, and 

 often provided with teeth on the inner margin. Walking 

 legs with the last joint short and robust, terminating in a 

 single claw. 



Range. — Warm seas, under stones ; in shallow and 

 deep water. 



Synopsis of the Species, 



A. Spines or teeth on inner border of fifth joint of first 

 pair of legs. 



