M A I I D E A. 77 



Legio II. PARTHENOPINEA. Corpus sive breviter triangulatum sive 

 valde transversum et antice arcuatum. Articulus antennarum exter- 

 narum Imus oculo interior, rarissime solutus saspius sutura infixus, 

 raro sine sutura externa coalescens. Pedea antici longiores, toti forma 

 normales. 



Legio III. ONCININEA. Corpus triangulatum. Antennae externae 

 e basi solutae, cylindricas. Pedes postici breviores, subdorsales, unci- 

 nato-prehensiles. 



The Oncininea form a transition to Dromia, and the Parthenopinea 

 to Corystes and Cancer. 



I. CRUSTACEA MAIINEA. 



IN arranging the Maiinea according to their natural families, we 

 are guided mainly by the characters presented by the orbits or eyes. 



In a large number of species, the eyes are retractile into proper 

 orbits; in others, they may be thrown back, or are retractile in fact, 

 but there is no orbit to receive them, and they are either exposed 

 when retracted, or are concealed beneath the carapax; in others, the 

 eyes admit of no retraction. The following are the families or groups 

 to which we are led : 



Fam. I. MAIII^E. Oculi in orbitis retractiles. 



Fam. II. TYCHID^E. Oculi retractiles sed orbitis carentes, infra 

 carapacem sese latentes. 



Fam. III. EuRYPODiDJi:. Oculi ad carapacis latus retractiles, sese 

 non latentes. 



Fam. IV. LEPTOPODIDJE. Oculi non retractiles. Pedes praslongi. 



Fam. V. PERICERID^E. Oculi non retractiles. Pedes longitudine 

 mediocres. 



In farther subdivisions, the position of the external antennae the 

 characters of the eyes in some cases, the characters of the beak the 

 form of the fingers, whether excavate spoon-like or not and the 

 greater or less length of the eight posterior feet, afford proper means 

 of distinction. The above families may thus be subdivided into sub- 

 families. In the following synopsis of the known genera of Maiidea, 

 we present these subdivisions and also the characters of the genera. 



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