ORDER DECAPODA PORCELLANA. 31 



Genus Porcellana, Lamarck. Body suborbicular or subquadrate. External antenna very long', 

 setaceous, placed behind the eyes; the internal concealed in cavities. Anterior feet very large ; 

 the carpus very long, with a lamellar prolongation. Posterior pair small and slender, folded 

 over the base of the others, and ending in a small didactyle pincer. Tail fan-shaped, bilamel- 

 late on each side. 



P. pilosa. (Milne-Edwards, loc. cit. Vol. 2, p. 255.) Shield elongated: front divided into three lobes, 

 of which the central one is triangular and prominent, the others small and rounded ; extremities 

 very hairy. Carpus middle sized, and armed towards the base of its anterior edge with a denticu- 

 lated lobe ; a few spines before this lobe. Hands short and wide; the following momLers almost 

 cylindrical. CoZor, brownish. Length, 0*5. Charleston, S. C. 



P. sociala. (Say, loc. cit. Vol. 1, p. 456.) Carpus and hand tuberculate before: tubercles very obtuse, 

 each composed of from four to nine granules. Anterior part of the thorax deeply crenate ; crense 

 inflected : in the two lateral ones are placed the eyes and antennte ; feet hairy. Length of thorax, 

 0*2. Probably the same with the preceding. Coast of Georgia. 



P. galathina. (Bosc, Hist. Nat. des Crust. Vol. 1, p. 233, pi. 6, fig. 2. Say, Ac. Sc. Vol. 1, p. 458.) 

 Shield flattened, striated longitudinally; pincers compressed; thighs dentate. This is all the infor- 

 mation we have respecting this species. From an inspection of the figure, it appears to have the 

 carpus strongly serrated, and the body and limbs punctate or tubercular; the length 0* 4. Bosc 

 states its habitat to be unknown, and Mr. Say merely cites the name, and states it to be common on 

 the coast of Georgia and Florida. Edwards does not cite it, but it may possibly be his P. pilosa* 



Genus Monolepis, Say. Shield convex, oblong, with a small rostrum. Eyes very large and distant. 

 Intermediate antennte stout, bifid at the end, and concealed under the rostrum. First pair of 

 feet didactyle ; the three following monodactyle ; the fifth very small, folded over the posterior 

 part of the shield, and terminating in long setm. Tail ending in three plates. A double series 

 of false swimming feet beneath the abdomen. 



Obs. This genus is composed of minute species. M. Milne-Edwards suspects that this and 

 its allied genus Megalops may possibly include merely the young of some other crustacean. 

 They form the passage from the Decapoda anomoura to the D. macroura. 

 M. inermis, (Say, Acad. Nat. Sc. Vol. 1, p. 157.) Front unequal, extended into a short rostrum, with 

 a tooth on each side near the eyes. A large truncate tubercle behind each eye. Tarsi simple. 

 Hind feet very small, terminated by three sette. Color, olive green. Length of thorax, 0'25. 

 Eastern shore of Maryland. 

 M. spinitarsus. (Say, loc. cit. Vol. 1, p. 58.) Tubercle behind the eyes obsolete. Tarsi armed beneath 

 with about seven rigid spines, of which the fifth is largest and tlie sixth smallest ; the tip incurved 

 acute. Length of thorax, • 3. Coast of South-Carolina. 



* Dr. Leach (_Nouv, Diet, des Sc. Vol. 18, p. 51) has arranged this and a few others under a subdivision of Porcellana, 

 which he calls Pisidia, but which has not been adopted by many subsequent writers, lie calls it Pisidia sayana, and 

 describes " the shield and pincers marked with short and transverse lines ; front trifid, with the elongated medial one itself 

 tridentatc and finely granular." The P. galathina of Bosc, is supposed by Dr. Leach to be difl'crent, and more closely 

 allied lo the sociala, and he adds the following characters : Shield striate ; front smooth and undivided ; pincers large, equal 

 chagrined above, with three very sharp spines on the inside ; hands nearly triangular ; fingers short, without any denta 

 tions within. 



