390 



CRUSTACEA. 



rent canal terminates at the middle, instead of the sides of the front 

 of the buccal area. The area is, therefore, produced and narrowed 

 forward, and the canal is generally a regularly formed channel, 

 covered quite exactly by the inner branch of the first maxillipeds, 

 which branch is narrow and much prolonged. These Crustacea are 

 thus widely different from other Brachyura, and the triangulate form 

 of the buccal area, by which they are distinguished, is the mark of a 

 fundamental distinction. They are brought together by De Ilaan 

 with the same limits and subdivisions as are here adopted, except 

 that he includes the Kaninidae, an Anomoural form ; the Corystidse, 

 a very different type, are excluded. The natural families are as 

 follows : 



1. Appendices maris geni ta les basi pedum btonim ortcc. [17a off' reus pone regio- 

 nem p>te rygostomianam ingrediens.^ 



Fam. I. Calappid^e. — Articuli maxillipedis extern! terminates non 

 celati. 



Fam. II. Matutid^e. — Articuli maxillipedis cxterni terminates celati. 

 3tio triangulate, palpo vix longiore epiam articulus 2dus. 



2. Appendices maris gmitales sferno ortcr. 



Fam. III. Leucosid.e. — Via afTerens apud angulum palati antero-late- 

 ralem ingrediens. Articuli maxillipedis extemi terminates prece- 

 dentibus tecti. Pedes postici ad normam gressorii. 



Fam. IV. Dorippim. — Via afferens parte regionis pterygustomiaine 

 postica ingrediens. Articuli maxillipedis extend terminates prece- 

 dentibus non celati. Pedes 2-4 postici subdorsals, prehcnsiles. 



The known genera of living species pertaining to these families are 

 distinguished as follows. 



Fam. I. CALAPPIDA]. 

 Subfam. 1. CALAPPINJE.— Pedes nulli natatorii. 



