l88 SMITHSONIAN MISCELLANEOUS COLLECTIONS 



than broad, with the lateral margins more or less acute and project- 

 ing", never smoothly rounded. The front is large, prominent, and 

 dentated. The orbits are deep. The first joint of the antennae is 

 large, joining the superior margin of the carapax, projecting within 

 in the form of a triangular tooth or point, and much produced out- 

 ward, far removing the movable joints from the orbit. The cheli- 

 peds vary in form, being sometimes broad and depressed, and some- 

 times narrow with a contorted hand ; the anterior margin of the short 

 carpus is generally prominent or unilobate next its juncture with the 

 meros. The dactyli of the ambulatory feet are of normal form, but 

 generally rather longer than in allied genera. 



A group of small species, with one of the hands much twisted and 

 its fingers excavated, shows some other dift'erences which serve to 

 distinguish it from the typical group founded on the P. platycheles 

 and similar forms. They might form a distinct genus (to which the 

 name Streptochirus would be applicable), but they are so intimately 

 connected with the others in the more essential characters that it is 

 thought best not to separate them here. 



The geographical range of the genus is wide, as it seems to be 

 represented in all seas of the temperate and torrid zones. It is the 

 only genus of its family which occurs in the European waters. 



The following known species belong to this genus : 



Porcellana platycheles Lamk. Porcellana dehaani Kraiiss. 

 sayil Gray. annata Dana. 



pilosa M. Edw. spinifrons M. Edw. 



ocellata Gibbes. suluensis Dana. 



longicornis M. Edw. 



295. PORCELLANA ORNATA Stimpson 



Porcellana ornata Stimpson, Proc. Acad. Nat. Sci. Phila., x, p. 242 [80], 

 1858. 



Carapax subovate ; surface anteriorly areolated ; protogastric and 

 hepatic lobules particularly prominent. Lateral margins obsoletely 

 2— 3-denticulated. Supraorbital margins deeply excavated. Frontal 

 region with a deep median sulcus. Front with a large median trian- 

 gular tooth with concave sides ; margins minutely serrated or dentic- 

 ulated. Chelipeds moderately broad and flat, nearly equal, sculp- 

 tured above with ridges, somewhat irregularly tuberculated ; beneath 

 obsoletely and distantly squamulated ; carpus oblong, quadrate, with 

 two longitudinal granulated ridges on its surface, and with its an- 

 terior margin straight and smooth except at its inner extremity, 

 where there is a small denticulated lobe ; posterior margin of the 



