CRUSTACEA OF ALABAMA. 43 



GENUS PLATYONICHUS. 



Platyonichus ocellatus, LainHk. 



The lady crab is also found in the waters of the Gulf of Mexico. It may be dis- 

 tinguished from the sea crab by being much narrower, not much broader than long. 

 The front lateral margins have five spines, front with a three-spined rostrum. 



FAMILY GRAPSID^. 



The little crabs of this family are chiefly found along shore and in brackish estu- 

 aries in the temperate zone. In general appearance they much resemble the fiddler crabs 

 with whom they consort. A few forms are pelagic and may be encountered far out at 

 sea. 



The carapace is subquadrate, flattened ; frontal plane broad ; antennules transversely 

 plicate ; epistome short, meropodite of external maxilliped bearing the palp at the exte- 

 rior angle or upon' the apex ; second joint of the abdomen of the male nearly as wide as 

 the adjacent portions of the sternum. 



The sub-family Grapsinse contains such species as have the antennae covered by the 

 front of the carapace. 



Genus Sesarma, Say. 



(Plate V, Fig. 3.) 



This is an enormous genus still very perplexing in the confused synonomy. The 

 species are scattered over the whole globe, at least exclusive of the polar regions. 



Carapace quadrate, nearly plane above, anterior margin excavated for the eyes at 

 the angle, lateral outline straight, posterior outline excavated for the bases of the limbs 

 of the fourth and fifth pairs ; antennae not cut off from the orbit, eye peduncles short, 

 outer maxillipeds with an oblique hairy ridge crossing outer surface of the ischiopodite 

 and meropodite, the latter rounded apically and elongate. 



It has been thought- best to carefully describe the species common in Mobile bay, 

 even though the name properly applicable may remain in doubt. 



Upper surface of the carapace little broader than long, proportions the same in both 

 sexes ; proportions as illustrated by the following measurements of an adult female. 

 Width 23 mm, length 21 mm, width of unemarginated portion being 11, distance be- 

 tween orbits 11, free lateral magin 13, distance from anterior margin to base of cheliped 

 10, length of abdomen of female 16, width 19, length of eye peduncle 4.5 mm. The 

 carapace ornamented by impressed lines and purplish splotches upon the olive brown of 

 the general surface ; pattern of impressed lines enclosing an oval space in front of the 



